You may donate freely, but right now it is illegal to sell a kidney. There is talk about lifting this restriction and allowing kidneys to be sold (we already allow paid plasma, sperm, and egg donation). If kidneys could be sold, it is estimated that one would sell for $50-$80k. We all have two kidneys, but most healthy people can live a normal life with just one. So, if you could donate one kidney and live with just one… would you sell and pocket the coin?