The explosion in college costs (which started in the 80s) is intimately tied to the student loan industry. It is a long and complicated story but, in brief, the easy access to student loans gave colleges (especially private colleges) a green light to raise prices up and up and up.
You can read more about it here
http://www.insidehighered.com/news/2009/05/05/collingeBear in mind there are legitimate costs to running a university: building & maintenance, recruiting and keeping faculty, staff, supplies, utilities, health insurance, etc. These costs never go away and they are constantly going up. Have you ever balked at your electric or water bill? Imagine what the electric or water bill is like for an entire dormitory (where almost no one pays attention to conservation). Now, imagine what the cost is for an entire campus with dozens of buildings from dorms, to libraries, to administration buildings!