What We Analysed

Ecommerce brands scaling Google Ads spend beyond £50k/month into six figures. We tracked revenue growth against marginal profit per additional pound spent, identifying where the relationship breaks down.

What We Found

Revenue continued to grow in most cases

The topline number kept moving in the right direction.

Marginal profit per additional £1 spent collapsed sharply

Each new pound delivered progressively less return.

The inflection point occurred earlier than leadership expected

Most brands hit diminishing returns sooner than their internal models predicted.

The Observed Pattern

£30k-£60k/month

Strong

Strong marginal profit. Each additional pound spent returns healthy incremental profit. Scaling feels easy and rewarding.

£60k-£120k/month

Flat

Flat marginal profit. Revenue grows, but profit per pound spent flattens. The business is running to stand still.

Beyond £120k/month

Negative

Marginal profit turns negative unless structure changes. Each additional pound spent actively reduces total profit.

Note: These thresholds vary by category, competition, and margin structure. The pattern, however, is consistent.

Why This Matters at Scale

At £20m revenue, small marginal inefficiencies destroy seven figures quietly.

A 5% marginal inefficiency on £1.5m annual ad spend is £75k in lost profit. At 15% inefficiency, it's £225k. These losses compound silently because revenue keeps growing-masking the decay underneath.

The Trap

Leadership sees revenue growth and assumes the model is working. Finance sees rising ad costs and assumes it's necessary for growth. Neither sees the marginal profit curve bending the wrong way.

By the time profit stalls visibly, the inefficiency has been compounding for months.

Conclusion

"Growth stalls not because demand runs out,
but because marginal profit turns invisible."

What Changes This

The inflection point is not fixed. It can be pushed higher through:

• Profit-tier account structures that isolate high-margin opportunity
• Spend governance rules that prevent budget leaking to low-incrementality demand
• Marginal profit tracking at the campaign level, not just account level
• Structural intervention before-not after-the plateau becomes visible

The brands that scale profitably are the ones that see the curve bending before it breaks.

The Marginal Profit Collapse Study