The author here insinuates that the increased cost comes from paying for teaching and research. But this is wrong for at least five reasons:
1. Research is not a cost center for colleges. It is a profit center. Usually, research is not funded by the college itself; rather, professors get grants from outside agencies, which the college then takes a large, juicy cut of for itself. (Ask any professor.)
2. At most colleges, the number of faculty members per student has remained stagnant for the last thirty years. The author waves their hands about "new areas of knowledge", but these new areas aren't leading to more hiring.
3. Wages for tenured faculty have also remained stagnant, adjusted for inflation.
4. Colleges are rapidly replacing their tenured faculty with adjuncts, who are given heavy courseloads, and paid peanuts even compared to tenured faculty (barely minimum wage, in a lot of cases).
5. Most of the actual work of research and teaching is done by grad students, of whom there are far more than tenured faculty. Grad students are, again, a profit center rather than a cost center, since the university gets to charge them "tuition" (despite most of them taking few or no classes). This "tuition" is either paid by an outside research agency, or "generously" waived in exchange for the grad student doing teaching and grading, again at very low wages.