The ACoS Deception

ACoS is useful, but it can mislead a Merch seller who reads it the same way an FBA seller does. Advertising Cost of Sales, usually called ACoS, shows the relationship between ad spend and attributed sales revenue. If a campaign spends $5.00 and reports $20.00 in sales, the dashboard shows a 25% ACoS.

In many Amazon advertising contexts, that number may look reasonable. A seller might see it and assume the campaign is healthy. For an Amazon Merch on Demand seller, that assumption can be dangerous.

The problem is not that ACoS is useless. The problem is that dashboard ACoS is calculated against the retail sale amount, not against the royalty the seller actually receives. A Merch seller does not keep the full price of a standard t-shirt, hoodie, sweatshirt, mug, or other product type.

The seller receives a royalty. That royalty is the real economic base of the campaign. That means the dashboard can show a sale while the business still loses money.

ACoS tells you what the ad spent against sales revenue. It does not tell you whether the royalty covered the ad spend. This is the first major economic trap in Merch PPC.

A seller can open the Amazon Ads dashboard, see orders, see attributed sales, see a seemingly acceptable ACoS, and still be operating below break-even. The campaign may look productive because it produced sales, but sales are not enough. The product needs to produce enough royalty to pay for the clicks that created the sale.

Consider an illustrative example using the US store. Assume a standard t-shirt sells for $19.99. If the ad campaign spends $5.00 to generate that sale, the Amazon Ads dashboard reports roughly a 25% ACoS because $5.00 of spend produced $19.99 of attributed sales revenue.

At first glance, that looks controlled. But the business result changes dramatically depending on the royalty group behind the sale.

Table 5.1. The Same Dashboard ACoS Across Royalty Groups