As late as 2000, there was a note posted on the women's room of my uni's chemistry building reminding men that it's a co-ed campus (for 40 years) and men's rooms were 1 floor up or down - they'd swapped alternate floor restrooms rather than add women's rooms. The costs of increased enrollment and diversity don't show up in instruction, but in physical plant, construction, and elsewhere. So does the increasing luxury of campus accommodations. Compared to the 80s, every building now seems to have its own coffee shop; quad dorm rooms are virtually unheard of; exercise facilities; crafting/maker spaces; etc.

Those things definitely go into tuition, fees, and residence costs, which is why (I think) it's important to separate the actual cost of instruction. One might imagine, as powerpoint and smart boards have replaced overheads and chalk, that instructional costs would inflate to accommodate all the new technology, but that doesn't seem to be so. At least in the few places I could find instruction itemized. Faculty salaries (broadly) have just kept pace with inflation.

Growing enrollment has really allowed state governments to mask their slow but steady per capita defunding of higher education.