The hospitals and doctors transplanting the organs in make a lot of money. Those harvesting the organs do not.

At least if it's aboveboard and in the US. Getting Steve Jobs an off the books pancreas would obviously have been exceedingly profitable. And I cannot speak to what happens in other countries.

But in general, the biggest cost is from the hospital stay for the recipient (the actual majority of it), followed by the surgery transplanting the organ itself. And, usually, the next cost will be transporting the organ, not acquiring it.