At least in California, where I live, and Alaska, where I went to undergrad, tuition increases in public universities are coming about because of increased numbers of administrators, expensive capital projects on campus, and decreased funding from the state.
As an aside, I used to be in the Air Force, and the base education office when I was serving had about a half-dozen legitimate colleges teaching classes on base, e.g., UC Davis, USC, Chico State, Chapman College, Yuba College, Southern Illinois are the ones I remember. Now it only has three providers on base - Yuba College, the local community college; Embry-Riddle, which is awfully specialized but considering it’s an Air Force base, you can understand why they’re there; and friggin’ University of Phoenix. I want to know who got bribed in the government to let the University of Phoenix replace all those other schools.