I suppose a single person with no debts whatsoever might be able to save 25% and live in a high rent area, or 50% and live in a lower cost of living area, assuming they are living in a no-income-tax state. But fewer than 25% of the population is debt free[1], and I'd guess the percentage of debt-free individuals capable of landing a $75,000 job out of college is even lower. Taking on any debt, or having any kind of "major" expense blows your computation apart.

[1] http://hosted.ap.org/specials/interactives/_business/debt_ad...).