How much money would it take to engineer biological immortality for at least half of the world's population, within 20 years, with 99% confidence?
No, even apart from greed no one has postulated such a system. Money isn't a perfect way to allocate resources, but no one yet has invented a better one, even assuming that people are perfectly altruistic.
How much money would it take to engineer biological immortality for at least half of the world's population, within 20 years, with 99% confidence?