The supply of kidneys does not meet the demand. As a consequence, the waiting time for a cadaver kidney continues to lengthen, and there is renewed debate about payment for living donors. To facilitate this debate, we studied what amount of payment would be cost-effective for society, i.e. what costs would be saved (if any) by removing a patient from the waiting list using a paid (living unrelated: LURD) donor-vendor. A Markov model was developed to calculate the expected average cost and outcome benefits of increasing the organ supply and reducing waiting times by adding paid LURD organs to the available pool. We found that a LURD transplant saved $94,579 (US dollars, 2002), and 3.5 quality-adjusted life years (QALYs) were gained. Adding the value of QALYs, a LURD transplant saved $269 319, assuming society values additional QALYs from transplantation at the rate paid per QALY while on dialysis. At a minimum, a vendor program would save society >$90,000 per transplant and provides QALYs for the ESRD population. Thus, society could break even while paying $90,000/kidney vendor.