Here's an interesting article on the economics of repugnance. As Sally Satel (and her donor, Virginia Postrel) have pointed out, an unwillingness to allow a market in kidneys is murdering thousands every year, to help ease the stomach of so-called biomedical "ethicists."
Note to Leon Kass, and others: the "yuck" factor, like all emotions, should be viewed as suggestions, not commands.
On one kidney, there are reasonable arguments about not having slavery be legal that do not turn on the "yuck" factor. On the other kidney, a cash market for one's first kidney donation, with decent regulation, could have substantially less abuse per sale than, say, the market for cars.