Why do sales and discounts make people buy things they did not plan to get?

Answer: A lower price feels like a gain, and a deadline makes missing it feel costly.

The store accepts a loss on each sale so shoppers can save money. — Promotions are not simply a gift funded by a loss on every sale. A store may earn less per item or use a loss leader while aiming to improve its overall business. A lower advertised price does not establish either a genuine bargain or a loss for the retailer.

A lower price feels like a gain, and a deadline makes missing it feel costly. ✓ — Discounts work mainly through the reference price: the old price makes the sale price look like a gain. A deadline or limited stock adds a fear of missing out, so people buy even when the item was not on their list. Stores may also set the original price with the discount in mind, so the bargain is less generous than it looks.

The products cost the store less during the sale, so the lower price is real. — A sale price does not prove that the store paid less for the item. Discounts can be planned into pricing or used to clear inventory, without any drop in the purchase cost. The reference price and time limit can influence buying regardless of how the discount is funded.