I was curious too, so I dug around and found this report from the Delta Cost Project, a nonprofit that studies this question (for US universities): http://deltacostproject.org/resources/pdf/trendsissuehighlig...

That is just the summary, there is a more complete report available too. The high points for me was that employee compensation accounts for 60-70% of costs, with increases there being driven by benefits (I assume this means health insurance costs rising), and that only 30-40% of that 60-70 is spent on instructional staff.