SEO or Paid Search: Where to Invest £100k?

For most established e-commerce businesses, the right answer is not an automatic £100,000 bet on either SEO or Paid Search.

The investment should go to the combination of channels expected to create the highest incremental contribution profit within the company’s cash-flow requirements, payback period and appetite for risk.

In practice, this often means using Paid Search to capture profitable demand that is available now while allocating enough budget to SEO to remove technical constraints, strengthen commercially important pages and reduce long-term dependence on auction-priced clicks.

Paid Search is usually the stronger immediate choice when profitable scale is available and the business needs revenue quickly. SEO becomes the priority when technical debt, weak category pages, poor indexation or excessive reliance on paid brand traffic is limiting future growth.

The central question is not simply “SEO or Paid Search?” It is:

Where will the next £100,000 generate the most additional profit—and what balance will protect both near-term revenue and long-term margin?

This article provides a commercial framework for making that decision.

Start with the next-pound decision

Historical channel averages can be misleading. A Paid Search account may report a strong average ROAS while the next £10,000 of spend produces a much weaker return. An SEO programme may appear expensive during implementation but continue generating value after the initial work is complete.

The decision should therefore compare the likely return from the next pound invested, not simply the average return reported across all previous activity.

Use:

Incremental contribution profit = (Incremental revenue × contribution-margin rate) − channel investment

The preferred allocation is the one expected to create the highest incremental contribution profit while remaining consistent with:

Cash-flow availability
Required payback period
Stock and fulfilment capacity
Growth targets
Risk tolerance
Seasonality
Implementation capacity
The business’s longer-term strategic position

This approach moves the discussion away from clicks, rankings and platform-reported revenue towards the financial outcome the company is trying to achieve.

Define the full investment in each channel

SEO is sometimes treated as free traffic, while Paid Search is reduced to media spend. Neither view gives a fair commercial comparison.

Paid Search investment should include:

Google Ads or Microsoft Ads media spend
Agency or in-house management costs
Shopping-feed management and optimisation
Creative and asset production
Landing-page development and testing
Analytics and experimentation
Promotions or discounts required to convert traffic
Relevant management overhead

SEO investment should include:

Agency, consultancy or in-house resource
Technical development and quality assurance
Category, product and editorial content
Design, photography and video where required
Digital PR and authority-building work
SEO and analytics tools
Website migration or template work
Relevant management overhead

If internal development and content costs are excluded from SEO, it may look artificially efficient. If Paid Search is judged only on media cost while substantial promotional discounts are ignored, its profitability may also be overstated.

The same commercial rules must be applied to both channels.

Attributed revenue is not incremental revenue

Both SEO and Paid Search can be over-credited by conventional attribution.

Imagine a loyal customer who sees a Meta advert, receives an email, searches for the brand and clicks a paid brand advert before purchasing. A last-click report may give the Paid Search campaign all the revenue, even though the customer may have bought without that click.

The same issue affects branded organic search. A customer already intending to purchase may search for the retailer by name and click the organic listing. The revenue is attributed to SEO, but the demand could have been created by brand activity, PR, email, retail exposure or previous experience.

Attribution answers:

Which touchpoint received credit for the sale?

Incrementality asks:

Would the sale have happened without this investment?

For a £100,000 allocation decision, the second question matters more.

Measure Paid Search incrementality

Paid Search should not be evaluated solely through platform ROAS.

Google Ads Conversion Lift is designed to estimate causal impact by comparing outcomes between treatment and control groups. Google reports metrics including incremental conversions, incremental conversion value, incremental cost per action and incremental ROAS.

Incremental ROAS differs from conventional ROAS:

Attributed ROAS = Total attributed conversion value ÷ ad spend

Incremental ROAS = Incremental conversion value ÷ ad spend

Suppose a campaign reports £500,000 in attributed revenue from £100,000 of advertising spend. The reported ROAS is 5.0.

However, a lift study estimates that £220,000 of the revenue would not have occurred without the advertising.

The incremental ROAS is therefore:

£220,000 ÷ £100,000 = 2.2

The campaign may still be profitable, but the investment case is materially different from the platform’s attributed 5.0 ROAS.

Where a formal lift study is not feasible, businesses can use:

Geographic holdouts
Campaign experiments
Brand-search suppression tests
Marginal-spend tests
Time-based tests with appropriate controls
New-customer-only analysis

The objective is to determine what additional value Paid Search caused—not simply how much revenue it claimed.

Measure SEO incrementality

SEO cannot normally be switched on and off as cleanly as paid media, but incrementality can still be estimated.

Useful approaches include:

Comparing optimised page groups with similar untreated pages
Tracking page cohorts by launch or optimisation date
Comparing actual performance with a documented baseline forecast
Using phased regional or category rollouts
Separating brand and non-brand organic performance
Adjusting for seasonality, stock, pricing and promotions

Use Search Console to understand pre-click performance, including impressions, clicks, queries and landing pages. Use GA4, the commerce platform and finance data to measure sessions, orders, revenue, refunds, margin and repeat purchasing.

The commercial SEO calculation is:

SEO ROI = (Incremental organic gross profit − SEO investment) ÷ SEO investment × 100

Do not claim every organic sale as incremental SEO value. Branded demand, returning customers and underlying market growth must be considered.

When Paid Search deserves the £100,000

Paid Search is normally the priority when the business needs revenue quickly and has credible evidence that additional investment can capture profitable demand.

It deserves the majority—or potentially all—of the budget when:

Profitable marginal scale is available

The key word is marginal. Existing campaigns may be profitable, but the business needs evidence that additional spend can maintain an acceptable contribution margin and payback period.

Review how performance changes as budgets and bids increase. If cost per acquisition rises sharply or incremental ROAS falls below the required level, the account may be closer to saturation than the headline average suggests.

The website converts effectively

Paid Search is more valuable when:

The product proposition is strong
Pricing is competitive
Stock is reliable
Delivery and returns are clear
The checkout works well
Mobile conversion is healthy
Product reviews and trust signals are present

Additional traffic will not correct a weak buying experience.

The business has a near-term commercial requirement

Paid Search can be particularly appropriate when:

Launching a new range
Entering a peak trading period
Clearing specific inventory
Supporting a promotion
Testing a new market
Replacing lost demand from another channel
Meeting a short payback requirement

The channel can be activated, tested and adjusted relatively quickly.

Shopping-feed quality is strong

For e-commerce businesses, feed quality can materially affect performance.

The feed should provide accurate:

Product titles
GTINs and identifiers
Prices
Availability
Product types and categories
Images
Variants and attributes
Promotional data

Budget should be allocated to feed and landing-page improvement where these are constraining profitable scale.

Brand and non-brand performance are separated

Strong branded performance can conceal weak customer acquisition.

Separate:

Brand Search
Non-brand Search
Shopping
Performance Max
Prospecting
Remarketing
Existing-customer revenue
New-customer revenue

This allows directors to see whether Paid Search is creating incremental demand or mainly intercepting customers already close to purchase.

The advantages of Paid Search

Paid Search provides several benefits when managed against commercial outcomes.

Speed: Campaigns can generate traffic and transactions quickly.
Control: Budgets, bids, targets, locations and products can be adjusted.
Testing: Feeds, landing pages, propositions and messaging can be compared.
Forecastability: Established accounts can often model short-term outcomes with reasonable confidence.
Demand capture: Ads can reach customers actively searching for relevant products.
Reallocation: Spend can move between products, campaigns and markets as performance changes.

The channel is especially valuable when the business has a short payback requirement or needs to understand demand before committing to longer-term organic investment.

The risks of investing the full £100,000 in Paid Search

Paid Search can also create vulnerabilities:

Platform attribution may overstate incrementality.
Branded campaigns can take credit for existing demand.
Cost per click can rise as competition increases.
Additional spend may produce diminishing returns.
Revenue can decline quickly when investment stops.
Automation can conceal weak product or query performance.
Short-term efficiency targets may restrict new-customer growth.
Overdependence on one auction platform can weaken long-term resilience.

The answer is not to reduce Paid Search automatically. It is to understand the marginal return and whether the channel is building profitable growth or simply maintaining an expensive dependency.

When SEO deserves the £100,000

SEO should receive the majority of the budget when the website is failing to serve existing organic demand or when technical and content limitations are suppressing long-term growth.

It becomes the priority when:

Commercially important pages are not performing structurally

Examples include:

Category pages are not indexed.
Faceted URLs create duplication and crawl waste.
Canonical tags point to the wrong destinations.
Internal links do not support priority categories.
Product pages rely on duplicated manufacturer content.
Discontinued products create dead ends.
JavaScript prevents important content from being rendered reliably.
Site migrations have left broken redirects or lost pages.

When the site already has product-market fit and search demand, resolving these issues can release considerable commercial value.

Existing pages have visible demand but weak performance

Search Console may show that category and product pages already receive impressions but rank poorly or attract a low click-through rate.

These pages may benefit from:

Better alignment with search intent
Stronger titles and page structure
Improved internal links
More useful product information
Better filters and merchandising
Clearer delivery, returns and trust information
Improved mobile experience

Optimising existing commercial pages is often more predictable than creating large volumes of content without established demand.

Organic performance is overly branded

If most organic revenue comes from customers searching for the company name, SEO may not be expanding discovery effectively.

Investment can focus on:

Non-brand category searches
Product-type and attribute searches
Comparison and buying queries
Specialist subcategories
Customer questions that influence purchase

The aim is to reach customers who were not already looking specifically for the retailer.

Paid-media dependence is eroding margin

If the business must continually pay for the same category and brand demand, SEO may strengthen margin resilience over time.

This does not mean SEO clicks are free. The business still incurs technical, content and authority costs. The advantage is that successful pages can continue creating value without a charge for every individual click.

The catalogue has stable, recurring demand

SEO is particularly attractive when the retailer has:

A broad product catalogue
Stable category structures
Recurring customer needs
Rich product attributes
Useful comparison opportunities
Sufficient margin and demand
Capacity to implement improvements

These characteristics allow investment to compound across many commercially relevant landing pages.

The advantages of SEO

Compounding value: Improvements can support performance beyond the initial investment period.
Non-brand discovery: Strong category and product pages can reach new customers earlier in the journey.
Margin resilience: The business can reduce dependence on paying for each click.
Broader website improvement: Technical and merchandising work can improve user experience and conversion across channels.
Coverage: A strong site can appear for large numbers of specific searches that would be expensive or impractical to target individually with paid campaigns.
Strategic asset creation: Content, architecture and authority remain part of the company’s digital estate.

The risks of investing the full £100,000 in SEO

Results can take months to mature.
Implementation may become trapped in a development backlog.
Forecasting is less immediate than Paid Search forecasting.
Search demand, competition and algorithms can change.
Weak content production may create volume without commercial value.
Technical recommendations may not be deployed correctly.
Attribution can over-credit branded organic revenue.
The business may need near-term cash flow that SEO cannot provide quickly enough.

Google states that some SEO changes can be reflected within hours, while others may take several months. It generally recommends waiting a few weeks before assessing whether a change helped in Search.

SEO therefore needs protected time and implementation capacity. It should not be expected to replace profitable Paid Search instantly.

A practical £100,000 allocation

For an established retailer with some profitable Paid Search activity and meaningful SEO opportunity, a sensible starting hypothesis is:

Investment area	Allocation	Purpose
Paid Search scaling and testing	£45,000	Capture immediately profitable non-brand and Shopping demand; test feeds, landing pages, bidding and query strategy
SEO technical and category-page work	£35,000	Resolve indexation, faceting, canonicals, internal links and template issues; strengthen category merchandising
SEO content and authority assets	£10,000	Develop buying guides, comparison content, product-led editorial assets and relevant digital PR
Measurement and experimentation	£10,000	Improve profit tracking, test Paid Search lift, establish SEO page cohorts and build decision-ready reporting

This is not a universal formula. It is a starting hypothesis designed to buy both short-term learning and long-term value.

The £10,000 measurement allocation is important. Without better evidence, the remaining £90,000 may simply scale whichever channel is best at claiming revenue.

When the allocation should favour Paid Search more heavily

A split such as £70,000 Paid Search, £20,000 SEO and £10,000 measurement may be appropriate when:

A seasonal peak is approaching.
The business has proven profitable marginal demand.
Stock must be converted quickly.
The website is technically stable.
Search coverage is already strong.
Cash must return within a short window.

SEO should still receive a protected allocation if stopping it would allow structural weaknesses or paid dependency to deepen.

When the allocation should favour SEO more heavily

A split such as £60,000 SEO, £30,000 Paid Search and £10,000 measurement may be appropriate when:

Important categories are missing from the index.
A migration damaged visibility.
Technical problems affect large sections of the site.
Paid Search marginal returns are deteriorating.
The catalogue has stable long-term demand.
The business can tolerate a six-to-twelve-month payback period.
Development capacity is available.

Paid Search can continue supporting immediate revenue while the organic foundation is repaired.

When the full £100,000 should not be released immediately

If measurement is unreliable, stock is unstable or neither channel has a credible forecast, release the budget in stages.

For example:

Allocate the first £20,000 to tracking, feeds, technical diagnosis and controlled tests.
Review early evidence and implementation readiness.
Release the next £30,000 to the strongest opportunities.
Reserve the remaining £50,000 for the channel and workstreams that demonstrate the best marginal return.

Staged investment reduces the risk of committing the entire budget to an untested assumption.

Compare SEO and Paid Search through the same framework

Decision factor	SEO	Paid Search
Time to first signal	Weeks to months, depending on crawling, indexation, competition and existing visibility	Days to weeks
Time to reliable ROI view	Commonly three to six months; longer for new domains or competitive categories	Often weeks to a few months where conversion volume supports testing
Best measurement approach	Page cohorts, forecast versus actual, matched-page controls and phased tests	Conversion Lift, geographic holdouts, campaign experiments and marginal-spend tests
Primary value	Compounding non-brand visibility and reduced reliance on paid clicks	Fast demand capture and controllable scale
Primary limitation	Slower ramp and dependence on implementation	Revenue often falls when spend stops
Main measurement risk	Branded organic demand is over-credited	Platform attribution and branded search inflate perceived return
Best suited to	Structural opportunity, stable demand and longer payback windows	Near-term demand, active testing and shorter payback windows

The objective is not to force both channels into identical behaviour. It is to compare their economic value consistently.

Use profit-based guardrails

Before spending, agree the rules that determine whether investment is increased, maintained or reduced.

Possible guardrails include:

Minimum incremental contribution profit
Maximum new-customer acquisition cost
Required payback period
Minimum first-order contribution margin
Acceptable LTV ratio
Stock-cover requirements
Minimum test confidence or evidence threshold
Defined implementation deadlines

Paid Search guardrails may be assessed more frequently. SEO guardrails should account for its longer maturity period while still requiring implementation and leading indicators to progress.

A 30-, 90- and 180-day investment plan

At 30 days

Confirm:

Purchase and margin tracking is reliable.
Brand and non-brand performance is separated.
Paid Search feed and campaign structure is suitable for testing.
Priority SEO technical issues are implemented or scheduled.
Important pages are crawlable and indexed.
Page cohorts and paid experiments are defined.
Stock and trading constraints are documented.

The first month should create a trustworthy decision environment.

At 90 days

Review:

Paid Search incremental or marginal returns
Performance by brand, non-brand, Shopping and customer type
SEO non-brand impressions and clicks
Priority category and product-page cohorts
Organic and paid conversion rates
New-customer acquisition costs
Implementation progress

Reallocate budget away from weak campaigns and SEO activities that lack evidence or deployment momentum.

At 180 days

Compare:

Incremental contribution profit by channel and workstream
Paid Search iROAS or best available lift estimate
SEO incremental gross profit and ROI
New-customer CAC
Payback period
Repeat purchasing and customer value
Brand and non-brand growth
Forecast versus actual performance

Fund the strongest workstreams more aggressively, subject to marginal return and capacity.

Five common allocation mistakes

1. Giving the full budget to the channel with the highest attributed ROAS

Attributed ROAS can reward branded demand, returning customers and conversions that would have happened anyway.

2. Assuming organic traffic is free

SEO requires development, content, authority, technology and management investment.

3. Treating average return as marginal return

The historic account average does not reveal what the next tranche of spend will generate.

4. Ignoring implementation capacity

An ambitious SEO investment cannot create value if development and content resources are unavailable.

5. Optimising channels independently

SEO and Paid Search interact. Paid query data can reveal organic opportunities; strong organic visibility can change the value of paid brand coverage; shared landing-page improvements can increase conversion across both channels.

SEO and Paid Search should share intelligence

The strongest model uses both channels as connected parts of a search strategy.

Paid Search can provide:

Fast query and product-demand data
Landing-page test results
Conversion signals
Geographic insights
Proposition and copy learnings

SEO can provide:

Broader long-tail discovery
Category and content opportunities
Search-intent insight
Durable landing-page assets
Reduced dependency on continually purchasing the same traffic

Shared reporting should identify where the channels reinforce each other, where they duplicate credit and where one can test opportunities before the other scales them.

Questions directors should ask before approving the £100,000

What incremental contribution profit is expected from each allocation?
What is the required payback period?
How much profitable marginal Paid Search demand remains?
Which SEO constraints are currently suppressing commercial performance?
How much revenue is brand versus non-brand and new versus returning customers?
What evidence shows the channels caused additional sales?
Are stock, pricing, fulfilment and conversion strong enough to support more demand?
Does the business have the capacity to implement SEO work quickly?
What will be measured at 30, 90 and 180 days?
Under what conditions will budget be reallocated?

If the answers are unclear, measurement and controlled testing should precede a large one-channel commitment.

The recommended answer

For most established e-commerce businesses, do not spend the entire £100,000 on SEO or Paid Search without evidence.

Use Paid Search to capture profitable immediate demand and test products, propositions and landing pages. Use SEO to remove structural constraints, expand non-brand discovery and build an acquisition asset that can strengthen margins over time. Protect part of the budget for measurement so the business can distinguish causal growth from attributed revenue.

A starting allocation of £45,000 to Paid Search, £45,000 to SEO and £10,000 to measurement is reasonable where both channels have credible opportunity. The precise split should then change as evidence develops.

At 30 days, validate the foundations. At 90 days, reallocate towards emerging winners. At 180 days, compare incremental contribution profit and scale the workstreams with the strongest marginal return.

The next £100,000 should not simply purchase more clicks. It should create short-term learning, profitable demand and longer-term margin resilience.

Frequently asked questions

Is SEO better than Paid Search for e-commerce?

Neither is universally better. Paid Search is generally faster and more controllable, while SEO can create compounding non-brand visibility and reduce reliance on auction-priced clicks. The better investment is the one expected to produce the strongest incremental profit within the required timeframe.

Should a new e-commerce business invest in SEO or Paid Search first?

Paid Search can test demand, products and landing pages quickly. SEO should still begin early because technical architecture and category structure become harder to correct later. A new business will often benefit from staged Paid Search testing alongside foundational SEO.

How much of an e-commerce budget should go to SEO?

There is no universal percentage. The allocation should reflect technical opportunity, search demand, implementation capacity, Paid Search saturation and the company’s payback requirements. A protected SEO allocation is valuable where organic constraints or paid dependence threaten future margin.

Can SEO replace Paid Search completely?

Usually not. Organic and paid results serve different roles, and Paid Search provides control for launches, promotions, seasonal demand and testing. SEO can reduce dependence, but removing profitable paid coverage indiscriminately may sacrifice incremental sales.

How should SEO and Paid Search be compared fairly?

Include the full channel cost, measure incremental revenue, apply contribution margin and calculate incremental profit. Use the same customer, refund and reporting rules across both channels.

What is the biggest risk when investing £100,000 in Paid Search?

The business may scale attributed revenue rather than incremental profit, particularly through branded search and remarketing. Marginal returns can also deteriorate as spend increases.

What is the biggest risk when investing £100,000 in SEO?

Implementation delays can consume the investment period before meaningful changes reach the market. SEO needs technical, content and development capacity as well as enough time for search systems and customers to respond.

Make the next £100,000 work harder

If your e-commerce business is deciding between SEO and Paid Search, Clubbish can build a channel-investment framework based on incremental profit rather than isolated platform metrics.

Our outcome-driven approach connects search strategy, measurement and commercial performance so marketing and e-commerce directors can invest with greater confidence.

Book a strategy call to identify how your next £100,000 can create measurable and profitable growth.