I think claims that this is done primarily for money are likely to be inaccurate.
Nobody continues an obviously highly dangerous practice “only” for the money.
I disagree strongly with the doc, but it’s pretty obvious he believes what he is doing is right.
Or, perhaps he needs to get up in the morning and explain himself all day to anyone who will listen that he's right. Probably deep in the recesses of his dark soul, there's a dying conscience imprisoned in a cage. He just needs to return to it constantly and recheck the lock.