Many of the arguments advanced by those in support of organ sales are actually valid: the choice is substantially indistinguishable from other choices permitted for different reasons; and any addition on donor organs to the very tight "market" of available donor organs would likely mean that one additional organ would become available to other potential recipients. However, the principal argument against the permissibility of selling donor organs is not the denial of those admitted benefits. Rather, it is a function of the inevitable consequences of wealth disparity and the traditional economic principles of supply and demand. Moreover, the fact that organ sales are permissible in other countries provides an opportunity to observe the actual consequences of that permissibility.

Precisely because donor organs for transplant are in such critically short supply, they would command a high price that only the wealthy could afford to pay. Since selling an organ is a considerably desperate means of earning income, only the relatively poor would choose to do so. This sets up a social and economic dynamic that exposes the poor to exploitation by the wealthy. This is precisely the situation that has already occurred in countries where organ sales are legal: in many cases, the organs of the desperately poor are purchased by the wealthy for the equivalent of only a few months' pay or even less (Levine, 2008). Beyond the natural economic dynamics of the market for donor organs, the poorest members of society would be especially vulnerable to exploitation by virtue of their comparatively lower literacy rates, education,...

Already, American society represents a critical differential in the availability of and access to health care based on wealth (Levine, 2008; Tong, 2007). The prospect of allowing the wealthy to purchase the organs of the poor would only exacerbate that differential. If the case study of a nation such as India (Levine, 2008) is any indication of the consequences, organs should never be allowed to be sold for monetary gain. Over the long-term and in the aggregate, doing so would harm society as a whole and expose the most vulnerable patient populations to abuse and exploitation, notwithstanding the short-term and isolated potential benefits in certain individual cases.
References

Beauchamp, T.L., and Childress, J.F. (2009). Principles of Biomedical Ethics 6th

Edition. Oxford University Press: UK.

Levine, C. (2008). Taking Sides: Clashing Views on Bioethical Issues 12th Edition.

McGraw Hill: Dubuque, Iowa.

Tong, R. (2007). New Perspectives in Health Care Ethics: An Interdisciplinary and Cultural Approach. Pearson Education, Inc.: Upper Saddle River, New Jersey.