The first number people see becomes the reference point for every judgement that follows. A price is never cheap or expensive in absolute terms — only relative to whatever came before it.
In 1974, Amos Tversky and Daniel Kahneman ran an experiment that unsettled the field of economics. They spun a rigged wheel of fortune — it could only land on 10 or 65 — then asked participants to estimate the percentage of African countries in the United Nations. The group who saw 65 gave consistently higher estimates than the group who saw 10. A random, irrelevant number had permanently skewed their answers.
This is anchoring: the tendency to rely disproportionately on the first piece of information encountered when making subsequent judgements. In pricing, it means the perceived value of any number is almost entirely determined by whatever number the user saw first. $79/year feels expensive with no context. It feels like a significant saving after seeing that paying monthly would cost $108. The product is identical. The perception is completely different.
Designers can use this honestly — showing a genuine reference price that helps users understand real value — or dishonestly, by fabricating an inflated “original price” that no one ever paid. Both use the same mechanism. Only one is a lie.
“Any salient number will anchor subsequent numerical judgements — regardless of whether it has any meaningful relationship to the question.”
— Tversky & Kahneman, Science, 1974
Both product listings below show the same flea collar at the same price: $47.99. The product, the rating, the features — all identical. The only difference is the anchor above the sale price. One anchor is the genuine previous retail price. One is inflated to manufacture a bigger discount. Notice how differently $47.99 feels in each context.
| Brand | Seresto |
| Duration | 8 months |
| Size | Large dogs (over 18 lbs) |
| Brand | Seresto |
| Duration | 8 months |
| Size | Large dogs (over 18 lbs) |
The mechanism doing the work is identical in both cases — a struck-through number above the real price that makes the real price feel smaller. The difference is whether the number being struck through describes anything real. One anchor is a reference. The other is a prop.
Fake anchor pricing is one of the most common dark patterns in e-commerce and SaaS, and one of the most frequently regulated. Beyond the legal risk, it carries a specific trust cost: once a user realises the anchor is fake — by checking whether the product was genuinely ever sold at that price — the entire credibility of the brand collapses. A detected lie about price is worse for conversion than no anchor at all.
The same three plans at the same three prices. The honest version anchors each annual price against the verifiable monthly alternative — users can confirm the maths themselves. The dark-pattern version invents an inflated original price no one ever paid, then screams percentages in red to manufacture urgency. The product is identical. The perception is not.
Every price on a page with a struck-through number should pass the same test: can that number be verified by a user who decides to check? The annualised monthly cost, a genuine previous price the product sold at for a period, a specific competitor's public price — these are all verifiable. A number chosen because it makes the discount look impressive is not.