Why is it that everyone looks for bargains or discounted items when

we go shopping? I look for the sales and clearance items as well. I know that I do not like to pay full price for certain items that I think are not actually worth the full price. Some things I understand you have to pay full price for because you kind of pay for what you get. But when does a store decide on what items are on sale, how long they are on sale, and when will they be discontinued or will the sale price be cut down to a lower selling price?