I was born in the Bay Area (San Jose), lived in West LA for college / grad school, and moved back to the Bay Area for work. I have no frame of reference regarding living outside high COL areas, but I've done so as both a poor young student, and now, reasonably compensated professional.
During the time I was in college, I lived close to campus, so I spent the vast majority of my budget (at times approaching 100%) on housing. At one point I made $25k a year, and I got by trimming all non housing expenses to a minimum. I spent ~$1 a day on food, didn't go out to eat, had almost no discretionary expenses, I had an old car which I repaired myself, etc. Later I found ghetto living arrangements to cut down on housing expenses to a few hundred a month. It wasn't luxurious, but one can adjust and make do. This is from someone who, just before starting college, couldn't imagine having a roommate, or living in anything other than a single family house.
Currently, real estate is significantly more expensive in both the Bay Area and Los Angeles compared to then, but I think the principle is the same; you make sacrifices, and after a while that becomes the new normal. While I make a decent living and could afford much more than I do spend, it's nice to live well within my means. I also have a family with a young child now, which constrains things a bit although not as much as one might expect.
At the moment total nondiscretionary expenses add up to a level where I'd be spending just every dollar of take home pay from $100k gross (taxes are high here), but there is room to cut and a significant portion of that is related to the high housing costs here, which are offset by generally high salaries. Nevertheless, even constrained by parameters like distance to work, it's possible to go quite a bit lower than most might think, although again, not without some compromise. I think I could live in LA with a similar quality of life for $60-70k gross.
When I tell people about some of my expenses, I get some initial skepticism (I've shown my $30 utility bill to incredulous coworkers a few times, and I have a new leased car for which total expenses including fuel, is <$250/mo over the life of the lease). The secret is, to find out what you really can do without and try to gain a little breathing room on multiple fronts - put off what you don't need immediately and seek out deals. Keeping up with the joneses in all aspects of life wears at your finances and unless you are truly well off compared to your friends and acquaintances, is generally a losing proposition which many people would acknowledge intellectually but which emotionally, is harder to get control of.
I have friends and acquaintances who make a fraction of what I do and because they are not careful about what they spend, spend everything regardless of what sort of raises they get at work, and are often in debt. I grew up in a comfortable upper middle class setting, but regardless of my economic circumstances (eg even as a teenager), always felt uneasy about the prospect of running out of money without a safety net, and so I always sought to have a financial cushion. Generally, I believe that if one is not proactive about such things, it's easy to get into cases where you end up overextending yourself beyond what you were anticipating, regardless of how much you make, where you live, etc.