As Unimpressive pointed out, that's the cost of tuition. The total cost (tuition + state expenditures + fees + endowments) per student has roughly paced with inflation over the same time frame -- and in some cases, dramatically decreased. You have to dig a little deeper to see those numbers, but several states have done their own analysis. Here's one for California:

http://keepcaliforniaspromise.org/wp-content/uploads/2013/12...

Seemingly nobody understands, or wants to understand this point.. College used to be an investment made by the working class in the youth paid for via taxes (state expenditures >> tuition), it's now flipped to an investment made by 18-year olds in their own careers (tuition >> state expenditures) -- Both approaches have their own merits, but focusing on cutting the cost of education misses the forest for the trees when those costs haven't increased over time.