[SilasX]

I think there are two phenomena here:

1) Opportunity cost: The land on campus, due to being near campus stuff, has appreciated a lot in value, so it doesn't make sense to use as dorms (instead of whatever else) unless you can charge out the nose for it.

2) Access to loans "for education" is easy to get, and this counts as part of the education package, so students figure to pay for not having to park or to walk as far.