My wife retired from a local university last year after 20 years. She had a Doctor of Education, the same degree Dr Jill Biden has. She was making about 1/3 what I did as a bachelor's degree in corporate America. The salaries are all top heavy, not the rank-and-file teacher, counselor, advisor, etc. The president of the university made more than the US President. They also had a Confucious Institute (aka Chinese spy organization) that was shut down. It funneled a lot of Chinese money into the system along with a lot of Chinese students.
$400,000 isn't a lot for an executive carrying the President's responsibilities. The original theory was that a successful man was successful because the United States gave him him opportunity to be successful. The successful business man would be "giving back" something to the country in which he had his success. The salary has always been set lower then it would be in industry for that reason. Unfortunately, "giving back" no longer seems to be the primary reason for people to run for the office. Power is the ultimate aphrodisiac.