[That might be why Sirius almost refuses to learn how it works, really. He mastered being an animagus at age 15, so muggle money should be no challenge at all, but then Remus might actually not go shopping with him and that's no fun at all.]

I have no idea what you're talking about, and I take great offense to the mere notion that I can't have everything I want.

[He sniffs, once.]

And you should get a new haircut. Something fun. Come on, it's not as though you have to impress any teachers, anymore.