ROAS is not a strategy

A campaign I ran in Kuwait hit 78x blended ROAS. It is the best number on my CV and it is also the number I trust least, because on its own it does not tell you whether the business made money.

What ROAS hides

Return on ad spend is revenue divided by spend. It says nothing about margin, nothing about whether those buyers would have purchased anyway, and nothing about how long the cash takes to come back. A 10x ROAS on a product with a 12% contribution margin loses money. A 2.5x ROAS on a subscription with an 18-month lifetime is excellent.

The four numbers I actually watch

1. Contribution margin after ad spend

Revenue, minus cost of goods, minus fulfilment, minus the ad spend that produced it. If this is negative, nothing else matters. It is the only figure that tells you whether the campaign added money to the business.

2. New-customer CAC, separated from blended

Blended CAC flatters you by mixing in people who were coming back anyway. Splitting acquisition from retargeting is the single change that most often reveals a channel is not working.

3. Payback period

How many days until the customer has repaid what they cost to acquire. This is a cash-flow constraint, not a marketing metric, and it is usually what actually caps how fast you can scale.

4. Marginal ROAS, not average

The question is never "what did this campaign return". It is "what will the next 1,000 currency units return". Average ROAS stays high while marginal ROAS collapses, which is why accounts look healthy right up until the moment scaling stops working.

What changed when I measured this way

On the Kuwait account, the headline ROAS stayed strong while marginal returns on one channel had already gone underwater. Reading the average would have meant pushing more budget into it. Reading the margin meant moving that budget to Shopping, where payback was 11 days instead of 34.

The uncomfortable part

These numbers need data most ad accounts do not have on their own: cost of goods, fulfilment cost, repeat-purchase behaviour. That means talking to finance and getting the ERP to hand you real margin per SKU. It is slower than reading a dashboard. It is also the difference between reporting on marketing and running it.