Why a higher ROAS can leave your business worse off

You've beaten the ROAS target. Finance would like to know why there's less money left. It's an awkward conversation, especially when the team has done exactly what it was asked to do. Spend came down, efficiency went up and the performance update looked great. The trouble is that a better ratio can leave the business with fewer pounds to pay people, cover overheads and fund growth. Before tightening the target again, it's worth checking what you're rewarding.

ROAS measures revenue attributed to advertising relative to the advertising spend. It's useful when the definition is understood and the target reflects the economics. But you can optimise the ratio while shrinking something the business needs. To judge the investment, look at the revenue and volume behind it, the costs that come with those sales and how much of the outcome the advertising actually caused.

The target improved. Contribution fell.

Consider two synthetic scenarios for a consumer business. Revenue is assumed to be net of VAT, refunds and discounts. Contribution margin before advertising is 40% after the variable costs included in this simplified example. Fixed overheads, tax and financing costs are excluded. To isolate the arithmetic, the example assumes the stated revenue is incremental to advertising and the scenarios are otherwise comparable. An ordinary platform report wouldn't establish that assumption.

Scenario B delivers a higher ROAS and £15,000 less contribution after advertising. That doesn't establish that Scenario A is always preferable. The business might have a cash constraint, limited capacity or a better use for the £55,000 of spend it avoided. You'd want to answer that before declaring victory in the trading meeting. The decision needs to account for the contribution forgone, the capital released and the opportunity to use that capital elsewhere.

Your highest-ROAS campaign could be the weaker investment

Now consider two hypothetical campaigns spending £10,000 each. Campaign A produces £60,000 of revenue at a 20% contribution margin before advertising. Campaign B produces £40,000 at a 40% margin. Again, these are simplified incremental revenue assumptions, with the same cost exclusions. Campaign A reports a ROAS of six and leaves £2,000 after advertising. Campaign B reports a ROAS of four and leaves £6,000. The lower-ROAS campaign produces three times as much contribution after media at that level of spend.

This distinction matters when product mix, discounts, cancellations or servicing costs differ. A platform optimising towards revenue has to work with the values supplied to it. Google's conversion-value guidance allows businesses to express values such as sales revenue or profit margins, but selecting a value doesn't automatically make the underlying measurement complete or causal.[1] The commercial task is to decide which signal represents value well enough, whether it can be supplied reliably and what important costs or future outcomes it misses.

Break even on what, exactly?

Under the simplified assumptions above, break-even revenue ROAS is one divided by the contribution margin before advertising. At a 40% margin, a ROAS of 2.5 covers advertising from contribution. At a 20% margin, the equivalent figure is five. These are break-even points after the specified variable costs and advertising, before the excluded costs. They aren't universal bidding targets, nor do they account for the business's required surplus, uncertainty or cash needs.

Apply that arithmetic to attributed revenue without assessing incrementality and you can build an entire efficiency story around sales that would've happened anyway. Add an optimistic lifetime-value estimate and the apparent headroom expands further. Future value deserves consideration, but it should come from credible cohort evidence, with an explicit time horizon, retention assumptions and payback constraints. An app install, a first order and a retained customer represent different stages of value creation.

The next investment decision is marginal

Even a campaign with strong contribution at its current spend might offer weak returns on additional budget. Demand, audience reach, competition and customer mix can change as investment grows. Equally, reducing spend to the easiest conversions may improve the average ratio while removing activity that still creates worthwhile contribution. A historic average can help frame the question, but it doesn't answer what the next pound will produce.

I'd bring three views into the decision: reported channel performance, customer or product economics, and evidence about incremental response. Where those views remain uncertain, set a bounded change with a defined review rather than assuming that either aggressive growth or tighter efficiency is automatically right. The recommendation should say what the business expects to gain, what it's risking and why the available evidence supports the choice.

It's frustrating to hit a target and still feel that marketing's contribution is being questioned. Sometimes the target deserves the scrutiny. A leadership team needs to know how investment changes valuable revenue, contribution and future opportunity within the business's constraints. Give the team a target that reflects those choices, and a fair account of what the evidence can tell you. Otherwise, you risk asking good people to deliver the wrong result more efficiently.

If your efficiency chart keeps improving while the commercial result disappoints, let's work through what's happening. GV Marketing connects performance metrics with customer economics so you can make a better decision about the next pound.

Read next: how to allocate your marketing budget when the reports disagree