ADVERTISING ECONOMICS · A WORKED COMPARISON
Same ROAS.
Different money left.
Two businesses can report identical ROAS and have opposite outcomes after ads because ROAS measures attributed revenue relative to advertising spend. It does not subtract variable business costs.
Here is a simplified example: two stores each report €30,000 in revenue against €10,000 in advertising spend. Both show 3x ROAS. Store A has a 50% contribution margin before ads; Store B has 25%.
Understand the numbers ↓AdsMath basic metrics check · First-order economics
Same reported ROAS
3.0×
Revenue / ad spend€30,000 / €10,000
At 50% contribution margin€5,000 left
At 25% contribution margin€2,500 short
Same ROAS. Different business.
Before fixed overhead and taxes. Illustrative figures.01 / The economics
Follow the money beyond the dashboard
| Metric | Store A | Store B |
|---|---|---|
| Revenue | €30,000 | €30,000 |
| Ad spend | €10,000 | €10,000 |
| ROAS | 3x | 3x |
| Variable costs excluding ads | €15,000 | €22,500 |
| Contribution before ads | €15,000 | €7,500 |
| Contribution after ads | €5,000 | −€2,500 |
| First-order break-even ROAS | 2x | 4x |
Store A has €5,000 available toward fixed overhead and taxes. Store B is €2,500 short before those costs. Calling both campaigns successful because they achieved 3x ignores the cost structure.
The calculationContribution after ads = revenue × contribution margin before ads − ad spend
02 / A worked example
Where the difference comes from
Product costs, fulfilment, shipping subsidies, payment fees and return-related costs can leave very different amounts from the same revenue. A discount can also change both revenue per order and the share available for advertising.
Use a consistent revenue basis after discounts and refunds, with consistent treatment of tax. Avoid double-counting refunded revenue as an additional cost. Margin should include the variable costs relevant to the order, not only the product purchase price.
03 / Read the numbers
Now compare the same stores per order
Assume both stores have 300 orders at a €100 average order value. Their ad cost per order is €33.33. Store A has €50 per order before ads, leaving approximately €16.67. Store B has €25 before ads, leaving approximately −€8.33.
Store A’s first-order break-even cost per order is €50. Store B’s is €25. The identical measured acquisition cost fits one business and exceeds the other’s ceiling.
04 / Scope and assumptions
What would Store B need to change?
Holding €30,000 revenue and a 25% margin steady, ads would need to cost €7,500 to reach zero contribution after ads. Holding revenue and €10,000 spend steady, contribution margin would need to rise to approximately 33.33% to reach that same point.
These are arithmetic scenarios. Cutting spend may also cut revenue; improving margin may affect demand. Reaching break-even still leaves no contribution toward overhead. Use the scenario to set a testable hypothesis rather than assuming the change will happen.
Scope: The comparison assumes a consistent attribution and revenue basis. Reported sales are not proof of incremental sales. Contribution after ads is not net profit, and total orders are not necessarily new customers. Repeat purchases and cash flow need separate evidence.
05 / The next decision
What should a campaign review include?
Keep ROAS, but add contribution before ads, actual cost per order, a target acquisition cost and the amount remaining after advertising. Then identify whether the gap is most sensitive to traffic cost, conversion, order value or variable costs.
Put the assumptions together with AdsMath
AdsMath by ScalingROAS combines an advertising economics Simulator with a Decision Guide PDF. Explore how traffic cost, conversion rate, order value and contribution margin affect modeled cost per order and what remains after ads.
€49 one-time. No subscription.
Explore AdsMath Simulator + Decision GuideNeed only ROAS, cost per order and average order value? Use the basic campaign metrics calculator. It does not calculate allowable CPA or contribution after ads.
