Isn't the whole concept of wizarding money self-contradictory?

There are possibly some rules in place to stop wizards from exchanging Muggle money (perhaps only Muggles or those from Muggle-born families are allowed to do it). There might also be laws against selling Transfigured items in Muggle shops. There could still be a way around such laws, but most wizards probably couldn't be bothered, and I can imagine pure-blood families like the Malfoys believing it was beneath them to associate with the Muggle world at all, even to make money.
It's an interesting thought though, and it would be nice to know more about the laws surrounding Transfiguration.

Well, someone would probably catch them, also inflation

Maybe you're the first to think of this.