I can tell you from the data from my school the administrative costs have gone up substantially. Both from number of administrators increasing significantly. The average administrative staff wage is over 250k (I know that's not a lot in tech salaries, but that is HUGE where I am. Cost of living calculator says $663,545 compared to SF). Our president makes 700k (just under 2m equiv) and gets 60k/yr salary increase.
I'm sorry, I just don't buy it. 60k/yr is more than the average lecturer at my uni makes. A lecturer! Not a professor. Even the CS Professors only make like $120k/yr (highest I see is 220k, which are the heads and are Full professors). So you are telling me that half the admins are worth at least twice as much as the CS professors (ones that are required to bring in money? And a substantial amount I might add). All our STEM professors are paid about that (CS is on the higher side) and all of them are required to bring in money and as far as I'm aware are paying for themselves (with equipment) and their students (all our masters get funded because all the PhDs are filling research positions).
I can understand lab costs going up but I think putting all the blame, or even the majority, on the professors is ludicrous.
And you also need to consider that hiring more professors doens't always equate to less income. You hire more professors to get more students (who pay a significant amount). I'll buy the argument of hiring professors in subjects that don't draw in enough students to justify their cost, but that's a different argument and I would argue is definitely not the lion's share.