This logical fallacy is cited over and over again. “Save 30% when you buy our product! Limited time offer!”
Suppose that the “normal” price is $100 and the sale price is $70. You don’t gain 30 dollars by not buying. You lose the $70 you paid for the “sale”.
If $70 is a good price, then the normal price is a ripoff at $100, and the company normally is overcharging customers. It’s dishonest to have a “normal” price that’s too high and have frequent sales. The most honest policy is to give your best price to all your customers. Superficially, you make more money cheating customers, but you will start losing customers when people notice.