Your Sponsored Display ACoS is probably lying to you. I just audited an account
By Liranhirschkorn · March 13, 2026 · Curated by George's Blog
Your Sponsored Display ACoS is probably lying to you.
I just audited an account where their CPM campaigns were showing 9-19% ACoS.
The CPC campaigns on the same products were over 40%.
Same audience. Wildly different numbers.
The brand looked at the CPM campaigns and said, "These are our best performers."
They weren't.
Here's a situational example:
You sell a winter beanie for $25. A shopper is browsing a competitor's listing. Your Sponsored Display ad appears at the top. She glances at it. Doesn't click. Keeps scrolling.
Later, she searches "winter beanie for women," finds your listing organically, and buys.
Your ad did nothing. But because she viewed it, Amazon attributes that $25 sale to your VCPM campaign.
Now multiply that across hundreds of shoppers.
Your dashboard looks like this:
SD - CPM campaign: 9% ACoS
SD - CPC campaign (same product): 42% ACoS
You think the CPM campaign is 4x more efficient. So you scale the budget.
But you're scaling spend on sales you were already getting organically.
You're not driving new revenue. You're paying for credit.
Amazon gives you the option to run Sponsored Display as CPC instead of CPM.
Switch them.
When you do, your "best" campaigns will suddenly look a lot worse.
That's not bad news. That's the truth.
Stop optimizing against inflated numbers.
Start optimizing against intent.