I agree with Walter Williams that there should be a free market for bone marrow. Especially if he's right that a donor's bone marrow regenerates within a few weeks.
I would question other sales if a donor's life was being put in jeopardy.
Some things I think can be thought of as proof that you are not of sound man and rejected outright.
But others like blood, bone marrow, and other parts are different.
We need an open-mind to discuss these issues and ultimately rely on good judgement.
At that foundation, should be strong moral values.
With bone marrow, preserving the life of the recipient should be the highest value.