Afaik, state schools have lost a lot of budget from states (in inflation-adjusted terms) compared to pre-90s.
Consequently, they balance the books by taking on more foreign/out-of-state students (who they can charge much more).
At the core, though, it appears to be a supply and demand problem: there's a ton of demand for people who want to go to college, colleges don't have the resources (or interest?) to expand supply, and so they raise prices because they can.
State schools have also been wasting a fortune on gold-plated facilities. I was just at UCSD yesterday and it was ridiculously nice. This is not a responsible use of tuition and tax dollars. We need an austerity program. If that makes the state schools less attractive to top students and professors then so be it.
This is moreso a problem with government/not-for-profit budgetary processes and capex vs opex.
With government funding, it's use-it-or-lose-it. I.e. state legislature will definitely allocate it to something else next year, if they come in under-budget in a year.
Add on top of that that state schools have the NASA problem: they're effectively performing (to state legislature and donors) for their dinner. And big, splashy buildings (with dedication names!) impress both. And attract picky faculty and students.
With not-for-profit, facilities are one of the few allowed places you can dump excess cash.
I floated in another comment that government grant/loan programs should impose an ACA-style admin vs teaching cost cap on institutions for participation. Maybe for capex too?
Consequently, they balance the books by taking on more foreign/out-of-state students (who they can charge much more).
At the core, though, it appears to be a supply and demand problem: there's a ton of demand for people who want to go to college, colleges don't have the resources (or interest?) to expand supply, and so they raise prices because they can.