In the post-war period the US spent a decent chunk of money via mechanisms like state sponsorship of universities and the GI-bill to ensure that university education was accessible to most Americans.
All of that spending took a downward turn somewhere in the 80s & 90s. As a consequence students must bear the vast majority of the cost of their university education starting somewhere in the 00s.
Universities began looking elsewhere for other sources of funding (since you can't actually run a university solely on the backs of students), and began reaching out for grants from the US government (NIH and NSF being two major funders). Now that gridlock in the Congress has forced the sequester on all of our federal institutions, we're seeing research dollars take a dive now too.
Private schools are part of the problem, but the real problem is that American politics has abdicated its responsibility to educate its people.
As a percentage of the total, yes, but I wrote this in another comment a few days ago:
Why Does College Cost So Much? is the most comprehensive treatment of the issue I've seen, and it argues that the main driver of college costs is Baumol's Cost Disease.
Universities like the University of Washington are also in a spending arms race: universities are increasing their per-student spending, even in the face of falling state spending: http://www.slate.com/blogs/moneybox/2013/06/04/public_univer...
Universities are in something of a prestige arms race, and that arms race is in part being enabled by subsidized loans that can't be discharged in bankruptcy. It's not clear that greater support from states would change this basic dynamic.
I'm most familiar with the University of California, where the state's willingness to fund it has massively decreased, not only as a percentage subsidy but in terms of actual contribution. In 1975, the state contributed $29k towards each UC student; in 1985 it was $31k; in 1995 it was $23k; in 2005 it was $20k; and today it's a mere $13k (all figures in 2012 dollars). That's a decrease of about 55% in per-student funding: http://www.kmjn.org/misc/uc_funding.txt
Overall cost of the UC system, on the other hand, has actually slightly decreased on a per-student basis, but not nearly enough to cover that 55% funding cut. Therefore, tuition has gone up to cover it.
If you want to factor out the confounding factor that a larger percentage of students go to college, you can also look at it on the macro-level and ask, what percentage of the state's resources do Californians choose to devote to funding higher education? That gives an indication of higher education as a public priority. And there it's again a drop of a little over half: in 1975 the UC system's funding equalled 0.3% of state GDP; today it equals 0.12% of state GDP. If funding were put back to 0.3% of state GDP (or even 0.25% or so), tuition could be cut almost to zero, so there is no real cost problem, just a no-longer-willing-to-fund problem.
Er, being a bit hyperbolic there aren't we?
It's a double-sided resource crunch. Funding is drying up, yes, but meanwhile costs as academic institutions are ballooning. Administrative costs have rocketed, while other changes such as increasingly generous tenure arrangements sap away resources from the cutting edge of education. It's not unusual for Tenured professors to get a sabbatical every three years, rather than the more traditions one in seven. In 2011, 20 of Harvard's 48 History professors were on sabbatical.
But in any case how much Ivy Leagues cost is hardly the main question of public interest; they could cost $80k for all I care. It's the decreasing affordability of systems like the University of California that is the major problem from a public-education standpoint, and that is mainly due to decreased funding.
Then by supply and demand, prices would have imploded since 2000. Either that or most schools went our of business. Right?
I think universities are like libraries: they are becoming obsolete in the age of the Internet. Knowledge is easy and cheap to access now.
That's a very good thing for an art school. Mediocre artists shouldn't be taking up the limit spaces.