Assuming it's not something they were shopping for in the first place...
The impulse big-sale buy is not a matter of acquiring a high value item they'll need later at a bargain price today.
No, the consumer is spending money in exchange for the feeling, right now, of saving big. The joy of a bargain. The item is secondary, the feeling is what we just paid for.
You wouldn't know that from the way people selling things act, but that's what we buy.
[Aside: More than a billion people on Earth have never purchased anything on sale at a store. The clearance-sale emotion is a learned one, and a recent one at that.]