It’s not infinite as some people might think, given the restricted supply. No, even with black market prices, it’s only about $200,000.
We need to make selling organs legal! The price would likely come down, but even if it didn’t, many people would be helped.
UPDate: Here is a link to a report on Medicare spending on dialysis. The per person per year cost of dialysis for Medicare patients (which is all dialysis patients owing to the quirk of Medicare that if you’re on dialysis, then you’re eligible for Medicare regardless of other factors like age) is about $85,000/year as of 2010. So it would be hugely cost saving to Medicare to pay for kidney transplants even if Medicare had to pay black market rates.