The lines represent the price in a given year, as a percent of the price in 1985.

This graph from the New York Times shows how much tuition has gone up, way more than other costs. College tuition and fees today are 559 percent of their cost in 1985. In other words, they have nearly sextupled (while consumer prices have roughly doubled)…

They offer several reasons, but since they are focusing mainly on state schools, public funding cutbacks appears to explain a lot of it.