Advertising that you are selling something at a discount is information that your price might be lower than a competitor. Nobody likes getting a discount at store A then seeing the same item for less at store B, and as a result, people don’t care much about discounts in an absolute sense. Only that the information announcement of the discount is advertising price competition with other sellers or substitutes.

When a seller lies about the original price to claim a discount, they are banking on consumers just “believing the lie” that the fake, pre-discount price was a competitive price compared with competitors or substitutes.

People choose to believe it’s a malicious & morally wrong action for the seller to do that, to intentionally play against consumers’ penchant to seek the lowest price among various alternatives by creating a discount from an inflated reference price that is intentionally not competitive with other sellers, and to hope that it fools some consumers who trust the seller instead of doing the legwork to compare prices & learn if the pre-discount price was in line with competitors.

People just choose to believe a seller that chooses to do this is shitty and acting antagonistically to manipulate buyers. They expect sellers to be honest about sources of price competition.

A discount should be with regard to a prevailing market aggregated price, or some close & sincere approximation from sampling the prices at competitors or prices of substitutes. If the discount is in regard to some other way of setting the pre-discount price, then it’s intentionally manipulating people to play on the cognitive flaw that they will nonetheless believe the discount is in regard to some notion of a “fair market value” price level, especially in situations driven by short-term cognition.