can't deal with the money talk

My bfs parents are offering to pay him a lot of money to lose weight. He's 22 and I'm upset because all his parents do is bribe with money. He's only 15 pounds overweight and he's trying to be healthy before they bribed him.  I love him for him. I can't stand his parents and them getting what they want cause they pay. He always only listens cause of the money. What do I do or say? I can't deal with it him saying that to me is honestly my breaking point. Please help.