The biggest lie in higher education is that "affordability" is a function of government subsidies rather than the cost of providing that education. Why should professors make $100,000+ per year for working less than 20 hours per week?
I suppose it depends on of what one is a professor. The ones in my family all work much more than 20 hours a week.
I suppose those who've never had to prep a class don't realize the 5-20 hours of development time which goes into a single hour's 'new' lecture? Not to mention the time spent in reading papers to grade 'em, counselling and advising students, attending assorted meetings, reading papers to keep up in the field, supervising labs, and attempting to fulfil the dictum of 'publish or perish'..... Oh, and making sure the textbooks are going to be there - after one has researched to select texts! And ordering lab supplies and .......
The 'question' above is rather like asking why ballerinas should get paid serious money when they only do three two-hour performances a week.