Clearance sales and going out of business sales really are a good deal sometimes. Clearance sales, particularly in clothing stores, are intended to get rid of items from the previous season to make room for clothes for the upcoming season. You've got to get rid of your sweaters and parkas sometime after Christmas to make way for short sleeves and capris for the summer (and vice versa). Many items of clothing are only considered "fashionable" for a single season so the stores really will slash the prices as the changing season approaches. I've bought summer shirts that were originally $40 for $5 in early September because of clearance sales. The store probably didn't even make money on that shirt but they wanted it gone so they could put other things in that space.

Similarly, going out of business sales are usually held to get rid of a store's inventory so they aren't stuck with it when their lease runs out. The last thing a store wants is to move a bunch of unsold crap so they will sell things for a fraction of the original price just to get rid of it before the closing date.

In both of these scenarios, the store will sell items for far less than they are worth just to get them out of the stock room. The reason they don't use those prices all the time is they'd go out of business.