A quote from Mankiw's excellent op-ed in the NYT:
Imagine that someone invented a pill even better than the one I take. Let’s call it the Dorian Gray pill, after the Oscar Wilde character. Every day that you take the Dorian Gray, you will not die, get sick, or even age. Absolutely guaranteed. The catch? A year’s supply costs $150,000.
Anyone who is able to afford this new treatment can live forever. Certainly, Bill Gates can afford it. Most likely, thousands of upper-income Americans would gladly shell out $150,000 a year for immortality.
Most Americans, however, would not be so lucky.