Some states have tied increased funding to tuition freezes or limited increases for in-state students. If the college increases their tuition by more than X%, they do not receive the additional funding.
Some PA. public universities have been playing an awful trick on their students. They claim they have not enacted a large tuition increase, but the standard semester tuition only includes 12 credits. If you want to take 15 credits a semester (which is what you need to graduate within 4 years), they charge you substantially higher tuition.