Nonsense. Saying that kidneys should be "commoditized" to avoid the black market it's like saying that slaves should be legal to avoid people travelling in a container.

In particular, kidneys can be transplanted from "dead" to living, and donning between living - even inside your family - is very restricted (at least in Uruguay). Although one case may be very altruistic and reasonable, there are thousands of subtle situations which are horrendous, and all the donning process will be heavily affected.

It's a moral statement: you can't put price on life or your body.

Improving the donors rate with policies is a better way to go and it hasn't reached its limits so far.