Daniel Akst has some good questions:
It's illegal in this country to buy or sell organs for transplant. This is an unjust law made and enforced by people who desperately need neither organs nor money. It condemns kidney-disease sufferers to death and potential organ donors to poverty. It's a law that I will unhesitatingly break if one of my children needs a kidney, and I hope you will have the decency to do the same if a member of your family is in a similar situation.
…The unearned piety of those who condemn these transactions strikes me as outrageous. If someone has the right to abort her own fetus, why does she not have the right to sell her own kidney? By what authority does the state tell me I cannot save myself or my family members by paying money I earned to a willing seller of a surplus item?