So you would rather force them to not send their kid to college and be in credit card debt for the rest of their life? If you are concerned about people being poor, help prevent them from being poor. Don't deprive them of whatever options they have left because you find it distasteful. They have to do something. If selling their organs is the best option, and they're not allowed to do it, they will just do something worse.

Besides, I don't understand why anyone finds it so horrifying. We indiscriminately implore people to donate their bone marrow for free, and we applaud those who do. But if they get paid for it, suddenly they are being exploited? And it would have been better if the leukemia patient died?

It's not the selling of organs that I find distasteful, it's the buying of organs. Or more specifically, patients not getting an organ because they can't afford one. That, and middlemen profiting from the organ trade without adding any life-saving value. But both of these things can be prevented by publicly regulating and funding the commercial organ drive.