This is very true.
Most of the full pay families that I know have two parents who are professionals (software engineers, nurses, a few doctors, …) who between the two of them make enough to be full pay, but don’t earn enough to be comfortable paying something close to $100,000 per year per child. This includes most of the people I happen to know. Also since the parents got professional careers by taking education very seriously and being very strong students, at least more often than not the kids are similar. Plus for some of these families the likely additional cost of graduate school is something that they need to keep in mind.
And there are a few families who had their children late, and have parents who are retired when the kids get to university age. When you are already retired and have been saving frugally for your entire life $500,000 sitting in a mutual fund looks like retirement funds to you, even if it looks like a college fund to the universities.
And there are lots of very good lower cost options, whether this involves in-state public universities or schools with good merit based aid or for a few of us universities outside the USA.
I see a lot of very strong students who avoid the highest cost highly ranked private schools because the cost has just gotten too high. This probably includes most of the families that we know. At least in our experience this does not seem to have harmed the student’s ability to do very well in life and optionally (if they want to do it) get into and attend highly ranked graduate programs.
This all seems like a high stakes game to me. Universities try to get these full pay families to pay the BIG bucks, and the families try to find a very good affordable alternative. At least in our experience the very good affordable alternatives are numerous. I expect that the highly ranked schools could say that the students who are willing to be full pay are numerous.