The last time I can remember a reasonably low rent payment, I was paying $300 a month in the year 2000 in Fullerton, CA. That was sharing a two-bedroom apartment between four guys, two of whom lived in the kitchen and living room and paid slightly less, one of whom was a speed addict and eventually got us kicked out and our lease terminated, which left me homeless briefly living in my car. No car payment because I'd bought it in high school for $260 at a sheriff's auction, but roughly $200 or in insurance plus gas money, mostly because commuting anywhere near LA/Orange county uses a lot of fuel. I was still on my parent's health insurance because you could do that until 25 as long as you were in school, and I wasn't paying back student loans because again, still in school. I was also 6'2" and regularly didn't crack 140 lbs because I was eating bulk oatmeal dry. I don't remember the cost of the shared phone bill, but I do remember it was under my name and that speed freak never paid his share, the bill eventually went to collections, and wrecked my credit for several years, which didn't really matter ultimately because I wasn't borrowing any money back then anyway other than the student loans.
I don't know a whole lot of 20 year-olds but certainly hear on the Internet all the time how hard it is for them. I'm extremely skeptical anyone living quite as shittily as I was 26 years ago is really paying 4.5 times as much for the privilege. My 24 year-old niece pays a lot more in rent than I did, but she also lives alone a mile from the beach in San Diego. In a shack, but it's still a hell of a lot nicer than anything I had.
In any case, I got a few bucks here and there from my parents, but they didn't have much when I was young and ultimately helped out my younger sisters a lot more. Cost of teenage parents, I guess. I was the test run. I still turned out fine and they've mostly relied on me in the past 15 years, which seems oddly missing from this survey. If we're concerned about adults not being self-sufficient, surely relying on your kids or siblings or anyone else at all is just as bad as relying on your parents.