Corrected entry: Monty Brewster needs to spend $30 million dollars in a months time and have nothing to show for it at the end. One of the stipulations is that he cannot destroy anything of value. There is a scene where he buys a valuable postage stamp that was printed upside down and then, so that he doesn't own it at the end of the month, mails a letter with the stamp on it. This would cause the stamp to no longer retain its value as there would be a postage mark on the stamp.
Correction: Postage stamps are valuable used too.
Except he doesn't own it since he used it for its intended purpose and now it's not in his possession. But, he didn't gave it away as a gift.
Correction: But he doesn't DESTROY it. It still exists. Moreover, he actually uses it for its intended purpose.