1) Living frugally doesn't have to suck. Being "I think I'll buy a new car today" rich doesn't actually make you any happier.
2) Retired means that you don't have to work if you don't want to. It doesn't mean that you have to sit around and do nothing.
3) Inflation is not ignored.
4) Most of the people here at HN probably can save $500k in 7-8 years, not 15.