How To Incent People Into Organ Donation: Possible Solution to Legal Conundrum

I've been thinking of a possibly legal way to encourage people to donate kidneys. Basically, people should be given the net present value of their donation around the time of their donation. This is to get around the legal problem of paying someone any "valuable consideration" for an organ donation. You are certainly legally allowed to pay for costs related to the organ donation process such as medical expenses, missed work, travel, etc.
I propose that paying everyone around the time of their kidney donation the lifetime expected value of medical costs relating to their kidney donation. For example, let's assume the costs related to the surgical removal of the kidney and related costs of missing work, etc. come to $20,000. Then let's say the person still has 30 years of life expectancy remaining. Also, assume that an annual CT scan, kidney function exam (creatinine level), and trip to specialists such as a urologist or nephrologist come to $2,000. Over the 30 years of the person's life that equals $60,000. Now add that to the $20,000 in costs for the time of the donation itself and you can give someone $80,000 and not really give them any "valuable consideration."
The economic underpinning of this plan is that people always discount the future. If I offer someone $1 today or $1 a year from now, it is rational for the person to take the money now because of reasons such as either of the people may be dead by then, the cost of uncertainty, and inflation.
Of course, purely altruistic donations are always welcomed, but we see that they cannot supply the levels of kidneys needed for the population.