dv8, there ARE places in the US where a family of 4 could live comfortably on $50k a year in 2012. It's a big country.
Once you get away from the big cities/states [California, NYC, NJ, CT, Chicago, etc.] it's doable. Real estate taxes are very low in some places, exorbitant in others. That's a big variable. A cousin in NC owns 1/4 of a mountain, and pays only hundreds in taxes. I have a postage stamp sized lot in NJ, and we pay about $8K. My brother on Long Island pays over $10K real estate taxes on a modest home. A condo in south Jersey pays about $3K in taxes, my parents' condo in Florida was $300 a year.
And like DR, it's a question of lifestyles. Home-cooked meals or lots of restaurants? TJ Maxx or Lord & Taylor? Hyundai or Mercedes? Cable TV or Live Concerts? Pollo guisado or Filete? .....on and on.....