There is declining support from the states over the last 20 years.
Costs are labor intensive, and there is pressure to use professors for more research rather than teaching.
There is an arms race to build the best facilities to attract the best students.
Current demographics - an increase in college bound students has increased demand for a basically fixed supply of schools, which generally aren't expanding capacity sufficiently.
The real cost is less than the sticker price due to increased financial aid, but the aid is not evenly distributed.