Kidneys, surrogacy, prostitution, gambling, price gouging, assisted dying: some transactions make people recoil, even when all parties consent. Cato’s Ryan Bourne talks with Nobel Prize-winning economist Alvin Roth about his new book, Moral Economics, what makes markets “repugnant,” what economists can add to moral debates, and why banning exchange rarely makes scarcity, exploitation, or hard trade-offs disappear.