The answer to the OP question has been posted at least twice - once the US government guaranteed repayment of students loans colleges increased their fees. This is the same reason healthcare costs are so high in the US.
As far as the discussion of whether or not college education has value or not, or whether education is right or privilege I suppose I have my own opinion. I earned 2 degrees. I think I learned more in college than in high school. College is basically sitting in a classroom for an hour listening to a lecture based on one or more books. students are then required to read the rest of the books on their own time as well as write papers with citations on those same books. Exams are administered to see if the student recalls facts and has a basic understanding of those text books.
Lecturing isn't teaching.
Not to oversimplify, but college is - 1) reading books, 2) passing examines on those books, 3) getting a piece of paper from an accredited college stating that you read all the books and passed all the tests. You pay for the diploma. Not for the education.
In my field of work some college may be required to apply, but a 6 month vocational school is required to obtain your state issued license. My job pays more to start than the attorneys in my office and the probation officers who have to have a Master's Degree that office in the same building.
I am all for education. I learned a lot in college. I continue to learn a lot by constantly having books to read.