Honestly, I think the budgeting thing is a huge portion.

I know that because I live similarly. I'm not big on going out to do things, and live incredibly cheaply otherwise. With a middle class job and no debts, I could easily just drop a grand plus a month on something without feeling a single change in my daily life.

Heck, considering how many of them live at home that would be a couple grand a month with no bills whatsoever.