Last month, 20-year old David Lomas donated over half of his liver to save the life of his father, Stephen. It was an inspiring sacrifice.
By Tim Harford
Presenter, Analysis: Repugnant Markets
Donated organs are in much demand
There aren't enough donors to go around, and 400 people die each year in the UK while on the waiting list for an organ transplant.
So what about a bit of basic economics here: if we want more live organ donors, shouldn't we pay people for their trouble?
To many people, the very idea is offensive. But is our disgust reasonable, or is it costing lives?
Our notions of what should be bought and sold have changed over time.
Life insurance, for example, was considered ghoulish until the early 20th century.
Now it is regarded as something that every responsible person should buy.
Yet there are still many transactions - anything from sex to a kidney transplant - that are viewed as beautiful in the context of a loving relationship, but corrupted by a cash payment.
So what should we make of a market for organs?
Dr Lee Rayfield has a unique perspective.
He has a PhD in transplantation immunology, but is also the Bishop of Swindon.
Bishop Rayfield argues that it can certainly be the right thing to donate an organ as a gift, but not for money.
"As soon as you introduce a transaction into giving a kidney, you have changed the whole basis of what's going on," he argues. Many people would agree.
Yet others argue that what really counts here is not the motive, but the results.
American writer Virginia Postrel has been campaigning for it to be legal in the US to pay cash for a kidney from a live donor.
She said: "People want to keep it as a heroic, uncompensated act because it makes them feel good.
"Never mind that tens of thousands of people are dying for your right to feel good about other people's heroic acts."
Postrel's criticism sounds cynical, but she isn't the cynic she appears to be.
She donated a kidney to a sick friend, became interested in the idea of a market for kidneys because of her experience with donation.
"The reaction is completely disproportionate to the actual risks involved. People do act like you're completely nuts."
Postrel points out that a market for kidneys could be regulated to ensure fair prices, safe operations and informed consent.
She also reminds us that kidney patients are disproportionately poor - and in the US, disproportionately from ethnic minorities.
If the idea of a market in body parts just seems appalling, I have bad news for you. Such markets already exist.
Professor Naomi Pfeffer, a sociologist and historian at London Metropolitan University, points out that the legal market for human bones and skin is far larger than any market for kidneys that might be set up.
She said: "Mrs Bloggs might agree to her head of femur being used by the hospital when she has her hip replacement operation and then unbeknown to her it will be handed over to one of the big commercial organisations which are processing bone and that company will then process it.
"And they've got catalogues showing the different size bones and you can buy it in powder form or pellet form or whatever. And they're doing that for money."
Professor Pfeffer's research shows that a corpse can be worth more than £100,000.
Some people could earn more dead than alive.
It's all very disconcerting. But there is an alternative way to match patients with donors: a so-called "Kidney Exchange".
Often, patients will have a family member or friend who is willing to donate a kidney, but transplant surgeons cannot carry out the operation because the kidney doesn't "match" and would be rejected by the patient's body.
A kidney exchange is a computer program that finds compatible pairs of donors and patients.
Al Roth, a Harvard economist who has helped to design a kidney exchange in New England, explains.
"I could give a kidney to your patient and you could give a kidney to my patient.
"So no money changes hands, but your patient and mine both get a kidney. That's a kidney exchange."
Roth's colleagues have already made 22 transplants using matches made through the kidney exchange.
Now the NHS division UK Transplant is setting up a similar exchange, and hopes to carry out the first paired donation within the next few months.
Even a kidney exchange won't be able to provide a kidney for every patient who needs one.
So will Virginia Postrel get her wish that other donors will be able to sell a spare kidney for money? Or will a cash market for live human organs always be a line that we refuse to cross?
BBC Radio 4's Analysis: Repugnant Markets, will be broadcast on 12 July, 2007 at 20:30 BST. The presenter, Tim Harford, is a Financial Times columnist and author of "The Undercover Economist".