The main driver of the growth of public education costs is legislative funding cuts. As government has stopped paying for higher education, this cost has been shifted to families, making what once was affordable, increasingly unaffordable. This crisis is is the result of choices we've made.
https://www.savingforcollege.com/article/how-do-state-fundin...
https://www.apmreports.org/story/2019/02/25/government-colle...
https://www.cbpp.org/research/state-budget-and-tax/funding-d...
1. Private non-profit universities are typically exempt from paying property tax. While this may seem like a reasonable idea, do note that many of these universities also own and operate commercial and retail centers, which complicates the tax exempt benefits. The ability to not pay tax is a direct subsidy from the local government to the university. One common and long standing story that illustrates this is the relationship between Yale and New Haven:
https://www.nhregister.com/colleges/article/Yale-s-tax-exemp...
Yale does pay some property tax, but really not as much as they should. They do actually make voluntary payments and New Haven is vastly better off that they're there, but they're still subsidized by the city and state.
2. The R&D departments at both public and private universities are heavily funded by the federal government. Note, only a fraction of the business that a university conducts relates to teaching students. One of its primary, central duties also involves research. The federal government funds both public and private universities and many private universities receive hundreds of millions dollars in such grants:
https://247wallst.com/special-report/2017/03/22/universities...
3. Pell grants, the GI Bill, and federal students are allowed to be given to private universities. In fact, for profit universities are supposed to limit their total income to only 90% of federal grants and most push right up against this limit. Without these government funds, they could not exist:
https://www.brookings.edu/blog/brown-center-chalkboard/2017/...
More generally, I'm not sure why the grandparent comment is getting as much grief as they are for laying blame on state legislators. The linked article from CBPP is pretty telling and damning. Candidly, the issue is complicated, but the state legislatures consistently decreasing funding the universities has made tuition raises inevitable. If anyone is interested, Pew has a recent article that has a lot of information that details the source of university funding:
https://www.pewtrusts.org/en/research-and-analysis/issue-bri...
There's a lot in there, but one of things they document is a shift from funding universities primarily through state funds to funding them through federal. Federal dollars are not just transferred to the university in the same way that state funds are. The law requires these funds be transferred through things like the GI bill, or Pell grants, or student loans, or some other vessel. Universities get access to these dollars by raising tuition. So, yes, federal student loans are a problem, but turning off that spigot doesn't magically mean the universities will have the money they need to operate. State legislatures should be held accountable for the problem that they helped facilitate.