Bioethics: bone donation and 3D parts

Parallel case (not today's prompt): One donor kidney becomes available, and several patients on dialysis are waiting for it. Should the kidney go to whoever can pay the most, or should something else decide?\n\nClaim: When a donor kidney is scarce, it should be allocated by a combination of medical need and likelihood of a successful transplant, not by ability to pay.\nEvidence: Kidneys for transplant can come from a living donor or a deceased donor, and many people with end-stage kidney disease depend on dialysis while they wait. Waiting lists are long because demand for donor kidneys is much greater than supply. Matching factors such as blood type, tissue compatibility, and how long a patient has waited affect whether a transplant is likely to work.\nReasoning: Allocating by medical need and likelihood of success sends the scarce kidney to a patient who both needs it and is likely to keep it working, which produces the most benefit from one organ. Allocating by ability to pay would let wealth decide who gets off dialysis, which is unfair because it ignores medical need and treats healing as something only the rich can buy.\nCounter-argument I heard and my response: A classmate said the youngest patient should always go first, since they have the most years of life ahead. That is a fair concern, but age alone can overlook a young patient who is a poor tissue match and an older patient who is a strong match. A better rule weighs need and likelihood of success together, and can consider age as one factor among several rather than as the only rule.