One of my rationales for participating in P2P is that bits aren't worth anything, so why should I pay for them?
I argue that if a musician wants to make money off their music they should come to my town and sing and dance in person.
I personally don't want to pay 250 dollars (or 2.5 dollars even) to see Madonna sing and dance, but at least she's charging for something that she is uniquely qualified to produce. In this sense she is justified in charging whatever she'd like.