Vouchers

Alice: A gift certificate is completely different from cash.
Dilbert: No, it's not. They're both pieces of paper you can exchange for goods and services.
Alice: You're missing the point.
Dilbert: Actually, a gift certificate is worse than cash, because you can only use it in one place.
Wally: And it expires.
Alice: At least it shows some thought.
Dilbert: It shows defective thought. You're trading perfectly good money for something that does the same thing, only not as well.