My father was an economics prof at a Canadian university. In canada a large part of the tuition cost is the actual professors. What the student pays doesn't even cover the professor salaries, the rest is made up by the government.
Consider that a tenured prof makes about 120k and teaches only 2 courses per semester, 2 semesters per year, while an undergraduate might have 6 courses per semester and pay 6-10k. My faculty had 2400 undergraduate students and while some classes in first year had 100 students, most were 20-30 students per class.
Outside of a few programs most tenured profs dont make anywhere near 120k. In my area, UMich is 80-100 and 2nd tier schools like Eastern Michigan pay 50-70. Getting a phd in most liberal arts fields does not pay, even if you manage to avoid adjunct hell.
Consider that a tenured prof makes about 120k and teaches only 2 courses per semester, 2 semesters per year, while an undergraduate might have 6 courses per semester and pay 6-10k. My faculty had 2400 undergraduate students and while some classes in first year had 100 students, most were 20-30 students per class.