How the Black Friday price check works
Every verdict on our tracker comes from prices we recorded ourselves, at the maker's own store, before the sale started.
The short answer
We record each product's selling price twice a day from the manufacturer's store. On sale day we compare the sale price with the lowest and median prices of the 30 days before. A deal is "real" only if it beats the 30-day low by at least 10%.
Where the prices come from
We read the public product feeds that manufacturer stores publish (TCL, eufy, Roborock and Dreame so far). Each record keeps the product and variant, the selling price, the store's compare-at price if it shows one, stock status and the time we checked. We do not use prices from pages whose terms forbid automated reading.
As of 2026-10-16, the dataset holds 14,954 price records across 1,297 product variants. You can download the snapshot.
How often we check
A scheduled job checks every feed at 00:00 and 12:00 UTC (09:00 and 21:00 JST). We add extra checks during sale weeks.
The verdict rules
| Label | Rule |
|---|---|
| Real deal | At least 10% below the lowest price of the previous 30 days |
| Small saving | Below the 30-day low, by less than 10% |
| Not a deal | At or above the 30-day low |
| Price raised before sale | The median price of the 7 days before the sale is higher than the median of days 8 to 30 |
| Not enough history | Fewer than 14 days of records for that variant |
We use the 30-day low because the EU's price indication rules use the lowest price of the prior 30 days as the reference for a "was" price (Directive 98/6/EC, Article 6a, as amended by Directive (EU) 2019/2161). US stores are not bound by that rule, which is why we apply it ourselves.
What we do not do
- We do not treat a store's "compare-at" or "list" price as proof of a discount.
- We do not include coupon codes, trade-ins or membership prices, because they are not open to every buyer.
- We do not get paid by any brand on the tracker. Affiliate links, if we add them later, will be marked and will not change a verdict.
Limits
We only see the maker's own store. A retailer can be cheaper. Feeds also list accessories and spare parts, and some variants go out of stock, so counts move between checks.
Questions or corrections: john@buyerdecision.com.