CTRebbe:
I would venture to guess that some have parents or others helping them with their housing or they are otherwise living in sub-standard conditions, which therefore enables them to afford some “luxuries”.
But it is not normal to need help from your parents, even when you are both working.
Regarding out-of-town, in most cases that means, maybe, as low as $300,000 instead of, say, $500,000, (figure $10,000 per year saved) and possible lower taxes (figure $5,000 per year saved), though usually higher tuitions would more than make up that ($15,000) difference.
Either way, it’s still insanely expensive. 40 years ago, salaries were not much lower than now, but house prices were less than just the down-payment is now. Meaning, say, $60,000 for a house, not $600,000. And taxes were also thousands less.
The bottom line is that unless someone else is paying the down-payment and perhaps even more than that, a middle-class typical frum family cannot afford to pay tuitions and buy a house in a typical frum area.