This is purely my unscientific, though information-based opinion... I graduated in 2000. Basically, an arms race started, as elite schools could afford to make it "free" to attend, others jacked up their tuition to become "elite" in their own way, online education was going to eat the bottom end (so to speak), and any college that wanted to stay in business had better ramp up their appeal. I think what you'll observe was beginning in about that time, there was a massive building boom, as each school tried to provide nicer dorms, facilities, etc in order to compete with other schools. Along with this was a significant boost in administrative overhead across schools, for reasons I've not quite understood - my guess is that in a drive to compete on quality, in came the middle management.
I do not know about all jurisdictions, but in my region of the world, the high school completion rate jumped by approximately 20 percentage points right around that time (from ~60% to ~80%). Assuming that holds true elsewhere, it stands to reason that with more people graduating high school, more people are likely to be accepted into higher levels of schooling. With more people attending higher level schools, the increase in demand (without an immediate increase in supply – it takes a long time to build new schools and even longer to recognize them as respected institutions), means price is going to rise.