“Comfortably” is certainly a matter of opinion. But that 17.3k is a purchasing-power parity average, targeted at HN’s largely rich-country leadership. The nominal average income per person in the world is 11.4k.
http://m.statisticstimes.com/economy/countries-by-gdp-capita...
So we have taken the usual cost of living adjustments into account, and the question is, do you want to live on the equivalent of 17.3k per capita US relative to the cost of living in most of the US — somewhere like, say, Pittsburgh?
It might make more sense to think in terms of a carbon budget if we are thinking about sustainability.
Growth doesn’t matter if it doesn’t reach the people.
The original comment point is that there is that growth is needed (but not sufficient) if one wants both conditions he pointed out to happen - which is most people.
By itself this is meaningless. What does it buy where you are? Most places that’s more than enough to live comfortably.
Anyway, money is only useful to decide who starves.