Right, there are a lot of administrators, janitors, technical support staff etc being paid by the university. But I'm surprised they aren't paid by the students tuition fees, since are so ridiculously high already.

There a too many administrators imo, who are often paid quite a bit. I don't think a University needs so many associate deans, assistant deans, and directors. Unfortunately it's people in those roles that make future hiring decisions so minimizing spending there isn't usually their goal.

Student tuition is high but not a high part of the budget. 40 years ago tuition was mostly covered by the state and tuition charged to students was basically just a copay to ensure you weren't terrible. But since the end of the cold war there's basically been a one way ratchet: every time a recession hits the states cut uni funding to balance the budget, the unis raise tuition to compensate, and when the recession is over this now the new normal.

The immediate question that would come from that is why is a technician or grant admin paid off tuition, when a student will never benefit from that?

That also doesn't account for things that don't "feel" like your typical university but are major research centers, like medical schools, where a lot of faculty are purely research.