Guide
Black Friday Discount Math: Spotting an Inflated 'Was' Price
A discount is only as real as the price it's measured against — and 'was' prices aren't always what they claim to be.
By Buğra SözeriPublished
Every big shopping event produces the same complaint: a “70% off” sticker that, on closer inspection, is 70% off a price the item was never really sold at. The discount math itself isn’t wrong — 70% off $200 really is $60 — the problem is upstream, in what number gets called the “original” price in the first place.
The mechanism
A retailer sets a genuine sticker price of $100 for most of the year. Shortly before a sale event, the sticker price is raised to $150 — briefly, and often without much visibility — and the sale then advertises “33% off,” landing back at $100. The customer pays the same price they could have gotten any other week, but the percentage badge implies real savings that never existed.
This pattern is specifically addressed by the FTC’s Guides Against Deceptive Pricing, which state that a former price used in a comparison should reflect a genuine, recently and openly offered price — not one invented or held only briefly to justify the discount.
The reverse-check
Given an advertised discount percentage and the sale price, the implied original price is:
original = sale price ÷ (1 − discount)
If a $60 item is advertised as “70% off,” the implied original price is 60 ÷ 0.30 = $200. If you’ve seen that same item sell for $90-$110 elsewhere most of the year, a claimed $200 original price is the red flag — not the $60 sale price itself, which might still be a reasonable purchase on its own merits.
Worked comparison
| Advertised | Sale price | Implied original | Plausible? (typical sale ~$100) |
|---|---|---|---|
| 33% off | $67 | $100 | Yes — matches typical price |
| 70% off | $60 | $200 | No — twice the typical price |
| 50% off | $55 | $110 | Yes — close to typical price |
What to actually check before buying
The advertised percentage is marketing, not the deciding variable. Before treating a sale event price as a genuine discount:
- Compare the sale price directly to what the item has sold for on other days, at other retailers, or via price-history tracking — not to the store’s own claimed “original” price.
- Treat unusually large percentages (60%+) on non-clearance, in-season items with more skepticism than modest ones — deep discounts on current merchandise are the pattern the FTC guidance is most directly aimed at.
- Use the reverse-check formula above; if the implied original price looks implausible for the product category, the percentage is likely inflated even if the sale price itself is fine. For the mechanics of finding an original price from any sale price and discount, see our reverse percentage guide.
Frequently asked questions
- How can a retailer make a discount look bigger than it is?
- By raising the 'original' or 'was' price shortly before the sale, then advertising a large percent off that inflated number. The dollar amount you pay might be reasonable, but the advertised percentage overstates the actual savings versus the item's typical selling price.
- Is this legal?
- It depends on jurisdiction and specifics. In the US, the FTC's Guides Against Deceptive Pricing say a former price used in a comparison should be a genuine price at which the item was openly offered for a reasonably substantial period — not a price invented for the sale. Enforcement and consumer-protection rules vary by state and country.
- How do I check if a discount is real?
- Compare the sale price to prices you've seen for the same item at other retailers, or to price-history tools that track a product's price over time. If the 'was' price is far above what the item has actually sold for recently, the discount percentage is inflated.
- Does a big percentage always mean a good deal?
- No. A 60%-off sale on an inflated reference price can cost more than a steady 20%-off sale on an honest one. The percentage tells you about the markup, not the actual price you're paying — compare the final price, not just the headline discount.
Sources & references
Authoritative references cited by this piece. Verified by Buğra Sözeri on the dates shown and re-checked at every deploy.
- FTC — Truth in advertising and price comparison guidance — Federal guidance on how 'former price' and percentage-off comparisons must be substantiated to consumers(as of )
- FTC — Guides Against Deceptive Pricing (16 CFR Part 233) — The specific FTC guidance on former-price comparisons and manufacturer's suggested retail price claims(as of )
Related
More guides on this topic
- APR vs APY: the difference that quietly costs you moneyAPR ignores compounding, APY includes it — and each side of the bank quotes the flattering one. The conversion formula, a worked table, and the disclosure rules behind the two numbers.
- Debt avalanche vs snowball: the math, the psychology, and a worked exampleAvalanche always wins on interest; snowball often wins on follow-through. A fully worked three-debt example with months and total interest under each ordering.
- What is a good ROI? Benchmarks, the annualization trap, and honest mathThe ROI formula, why comparing un-annualized returns across holding periods is meaningless, historical benchmarks with sources, and when a high ROI is a red flag.
- How inflation is calculated — and what it quietly does to savingsHow CPI baskets work, the compounding purchasing-power loss on idle cash with worked tables, nominal vs real returns, and the rule of 72 for halving time.
Published September 25, 2026