So any additional growth in life expectancy will probably be exponentially more expensive That's true exactly because we haven't addressed the root problem of

So any additional growth in life expectancy will probably be exponentially more expensive That's true exactly because we haven't addressed the root problem of aging. If everyone could be restored to the physical condition of a 25 year old, medical costs would fall tremendously. Which is one reason why "only the rich will be able to afford it" is unlikely; governments and insurance companies would probably profit by making anti-aging treatments free. If you look at Japan or the US, the increase in life expectancy has coincided with a drop in the birth rate - which leads to a situation where you have a lot of old people, but relatively fewer younger workers to support them than in the past. Likewise, this is only a problem because aging eventually results in the inability to be economically productive.