The "Value" Argument(s)
Multiple posts debate Monty getting value for his money. If the quotes page is correct (I haven't seen the movie in a while) then there are a lot of confused people.
The rules he was given says he "can hire anybody you want, but you have to get value for their services". He can give 5% to charity and gamble the same amount but he can't just give the money or objects away, "buying the Hope Diamond for some bimbo as a birthday present". He can't destroy "what is inherently valuable". The rest of the rules are about telling people, time limitations, etc..
He hires a lot of people but they all provide him a service of some kind, hence "value" for their services. Yes, he's overpaying them but for some of them, you might reasonably argue that others are compensated similarly. There are some photographers that are highly paid for their work as an example.
The biggest issue is over the stamp. You have to take into consideration the two different uses for the stamp. First, it is a collectible. It was a misprint and is rare so on the collectors market it is very valuable. Second, and more importantly, it is a postage stamp. It's meant to be used to mail something. In this case Monty paid what the stamp was worth then used it to mail the postcard. Once he put it in the mail it no longer belonged to him and since it was cancelled, it no longer had value to do it's intended purpose.
I've always wondered why he couldn't buy something very expensive, like the Hope Diamond, then turn around and sell it on the open market for next to nothing. He wouldn't be giving it away, he would be getting back what HE considered the value to be. As long as this was done as an "arms length" transaction it should be within the rules.
I'll have to watch the movie again to verify the rules but I don't have any reason to doubt the quote on imdb.