I think for the living paycheck to paycheck you do have to look at lifestyle. I know people who make $250,000 a year who live paycheck to paycheck.
Class distinction to me has alot to do with where you live and how many kids you have. Someone here said they live high on the hog on their salary, but they have no children. For the many opportunities you may want to give your kids, the costs are significant. 14 years of Catholic school and piano lessons means I drive a very old car, rarely go out to eat, and only go on one small vacation for a couple of days per year. By the time they hit high school, these 2 things alone run $10,000 per year per child. It means my kid has no car but to me the education was more important. I could surely live a "higher" standard of living if I spent that money on an iPhone, a new car ... but I am fine without them.