I don't really like these sorts of stories where some socially-incompetent otaku takes advantage of an honest girl. He didn't seem to realise that she'd fallen in love with him, and instead of choosing to have a loving relationship decided that he'd rather do the pathetic "I am your master!" thing.
Ah yes, prostitution to raise money for a personal reason + rich kid who takes full advantage of it.
Quite the tactic he employed though, inviting his 'friends' over to treat her roughly just so he can be gentle with her afterwards, which caused her to come to like him and thus, her training is complete.
I'd say he should at least pay off her debt, as a token of goodwill or...something. I think there could have been an option for not only getting the money to cover the debt AND stay in this relationship with him, but I suppose it wasn't meant to be.
Hell of a way to make cobbler.