https://www.collegetuitioncompare.com/statistics/
Anecdotally, the college I went to, New College of Florida, is a public liberal arts school whose costs aren't too far out of alignment with other state schools in Florida. According to their fees page, in-state tuition fees, room and board would total $16K a year; for out-of-state students, that would be $39K a year.
https://www.ncf.edu/admissions/tuition-and-fees/
Actually, I'd like to gently question your figures: you're indicating your kids are paying $2000 a semester -- so that would be $4000 a year, or $16,000 over four years. And you're saying that doesn't include their tuition, so that's just room and board, right? (That's under half the cost of New College's, which again sounds like quite a deal.) Further, room, board and tuition at this private college would still be under $20,000 over four years? Unless I'm missing something, that would mean tuition at this private school is less than $500 a semester. I can't help but suspect that either one of us has our math wrong, or you have the best school deal in the history of ever.
I too am very interested in the answer to this question. if you're spending that much and not going to a top 30 school, you're a chump. if you are going to a truly elite school, you're not paying anything close to the sticker price unless your parents are quite well off.
I'm not saying college isn't unreasonably expensive these days, but I often see this number for undergrad and I always wonder where the hell it came from.