JAMA published an article in 2002 showed that most of the donors are poor people in debt and a few years later they are still or again in debt and have experienced a decline in health. An essay in Lancet the following years details the global organ traffic and some of its negative consequences.
Despite these horrors they abysmal supply of organs makes the concept of buying and selling organs appealing. I have confidence that a well regulated market place for organs could improve the supply and avoid the horrors which result from the under-the-table, unregulated bazaar that currently exists.
Sally Satel outlines the pro argument in a couple of essays.