It's not greed, it's just how business works. If she has any sense, she'll slowly up her prices until the demand drops off, and then drop them a bit to find a 'sweet spot' of amount of work for amount of money.
I raise my prices as often as possible, because the more money I make, the more whoring I can do. Of course, if I am working too many hours to make that money, I won't have the time or energy for whoring, so a balance has to be struck. I'm sure our well-endowed friend is doing the same (the money I mean, I'd be surprised if she spends it whoring).