Of course, this is exactly how a monetary economic system works. It is trading one resource for another. Money is very useful because sometimes you want something but don’t have anything the other person wants; or you do, but there’s no easy equivalent trade.

In this case, kidneys are pretty equivalent, so trading can be done effectively. Still, it’s really no different than using money, except that it prevents people from making a kidney equivalent to anything but a kidney. This really sucks for you if you don’t have anyone that loves you enough to give you a kidney. In this case, money can’t buy you love… or your life.

Still, this is a great improvement if you are lucky enough to have caring relatives.