"Was $99.99, now $39.99." It looks unambiguous. It almost never is. The way retailers compute the strikethrough price is governed by a thin layer of consumer law, a thicker layer of retailer policy, and the loosest layer of real-world practice. Here's what's actually behind the number.
What the law says
In the US, the FTC's Pricing Guides require that an advertised "regular" price be one at which the item was offered "openly and actively" for a reasonable period. In the UK, the CMA's Pricing Practices Guide says the higher reference price must have been the most recent selling price for at least 28 consecutive days in the prior six months. Australia's ACCC and Canada's Competition Bureau have similar but not identical tests.
What this means in practice: a retailer can legally call a price "regular" even if very few units sold at that price, as long as the listing was "available." The bar is meaningfully lower than most consumers assume.
How retailers compute "Was"
Three common methods:
- MSRP / RRP — the manufacturer's recommended price. Often dramatically higher than the price the retailer ever charged.
- Highest list price in 90 days — common on Amazon. The "highest" price may have only existed for one day.
- Median selling price in 30 days — used by some department stores. The honest one.
How third-party trackers work
Tools like Keepa, Honey and DealsHub poll product pages on a schedule and store the prices over time. The granularity varies — Keepa is hourly on top SKUs, daily otherwise. The honest signals you can extract from a price-history series:
- 30-day low — the floor recently. If the current price is at or near it, the deal is real.
- 90-day median — the price most people actually paid recently. Compare the current price to this, not to MSRP.
- Price stability — flat lines mean static demand. Sawtooth lines mean someone is repricing aggressively (often algorithmic).
What we do at DealsHub
Our Deal Score (0-100) weights the discount-vs-90-day-low at 50% — meaning a fake 70%-off based on inflated MSRP scores like the 18%-off it actually is. We surface the 30-day low and 90-day median in the deal detail view so you can sanity-check our verdict.
The honest summary
Don't trust strikethrough prices. Trust price history. If you must shop without a price-history tool, the safest mental model is: assume any "60% off" is really "20% off" and shop accordingly. You'll be right more often than wrong.
Set a watch on any deal you're tracking — when it hits a new 30-day low, you'll get an email.