“Our revenue numbers were amazing, and everyone was celebrating, but then I realized we hadn’t made any money at all. Actually, we had lost money.”
That’s a tough way to learn that revenue doesn’t equal profit, especially when margin is low due to discounts and ad spend and costs are elevated.
With Prime day moving from July to June 23-26 this year, here is how smart marketers will maximize revenue when margins are thin and ad costs are high to preserve profit.
| About the Data: We analyzed 90 U.S. brands during the 2025 Prime Day window, defined as June 28 – July 21 (peak days July 8 – 11). Pre, during, and post periods reflect the 10 days prior, the event days themselves, and the 10 days following. E-Commerce spend refers to paid media directed outside the Amazon ecosystem. Revenue figures reflect incremental gains via Measured's proprietary incrementality testing. Reported in aggregate; individual brand results are strictly anonymized. |
First, it’s important to look at what has happened during past Prime Days.
In 2024, Prime Day was a 2-day event (July 16-17) concentrated, frenzied. And brands overspent, massively.
- Average spend per day increased 236% year over year
- Incremental revenue, on the other hand, dropped 20% year over year
- In the post Prime Day “hangover” incremental return on ad spend (iROAS) on Amazon dropped 18%
In 2025, Prime Day was a 4-day event (July 8-11) Amazon’s longest Prime Day ever, our brands took a huge step towards right-sizing their ad spend.
- Average spend per day still increased, but just by 32% year over year
- Incremental revenue increased 66.9% year over year
- The post Prime Day “hangover” iROAS on Amazon was almost non-existent, down just 3%
What does it all mean?
Do not over invest. With another 4 day event similar to 2025, the single most important marketing metric on Prime Day is your marginal incremental ROAS. This is the north star for goldilocks spend. To get reliable marginal metrics brands need Media Mix Model to get seasonally calibrated response curves, ideally calibrated by incrementality tests.
For brands without access to the tools needed to determine marginal incremental metrics, do some back of the napkin math.
- As you increase your spend, keep an eye on how many more sales you get above baseline per additional dollars spent above baseline.
- Example: If you usually get 100 sales per day at a $10 CPA and you increase your budgets to $2,000 per day and see 120 sales, the marginal CPA is $50. Don’t be tricked into spending more by the $17 CPA.
- These aren’t marginal incremental metrics, so the reality is likely that your incremental cost per acquisition (iCPA) and marginal iCPA are worse, but at least it will prevent a 2024 like disaster.
How should brands spend on ads driving to owned e-commerce sites during Prime Day?
The data is quite clear: pulling back has no upside.
Looking at the periods directly before and during Prime Day in 2024, 24% of Measured brands pulled back their e-commerce driving ad budgets and saw iROAS increase by 12%, however they lost nearly half their daily incremental revenue.
By 2025, 68% of brands pulled back and the efficiency gain disappeared too, leaving only an incremental revenue decrease.
In both 2024 and 2025, keeping spending flat was the best move.
Protecting your e-commerce and retail revenue and customers is extremely important. Every customer you convert on your site instead of Amazon is materially more valuable due to higher margins, an owned relationship, and valuable first party data.
Prime Day is becoming a multi-day browsing event, not a 48-hour frenzy. Brands that win in 2026 won’t wait for Amazon to create demand on their site and rush to capture it with ads.
You reap what you planted. Prime Day is the harvest—not the time to start seeding.
Profit works the same way. Brands who win on Prime Day will win because they set themselves up long before Prime Day with high intent audiences.
The data-based Prime Day strategy?
Let the event and the discounts bring in sales. With margins already low, spending money on expensive ads on Amazon and driving to Amazon will only eat into your profit without generating additional sales. Instead, support your e-commerce budget and acquire higher value, higher margin customers.