Interestingly, Iran is the only country in the world that allows its citizens to pay for someone to give up their kidney https://en.m.wikipedia.org/wiki/Kidney_trade_in_Iran.

By some accounts it works rather well, see http://www.econtalk.org/archives/2015/09/tina_rosenberg.html.

(It is true that they do allow other nationalities to pay for a kidney, however someone of their own nationality must give up the kidney, preventing at least some level of medical/tra splant tourism).