My wife is a 43 year old Professor of Biochemistry (Ph.D. Texas A&M, 1995); works at a 15,000 student State University.
She is tenured.
Salary = ~$70,000; Full professors at this University, with 20 years in are 6-figure.
Science doesn't increase or decrease her salary; the professors have a union (APSCUF); so ALL profs make the same; I have tried to explain to the Science professors that they are getting screwed in this deal; but they don't get how they are more rare (and valuable) than an English Education professor. The high school science teachers in our district ALL out earn her.
Regardless; most of them do what they do because they like/love it. Most made a choice to NOT go to medical school after undergraduate work - because they wanted to do research. As it turns out, at least at this school, with full teaching loads, they spend most all of their time (not hyperbole; my wife works a 90 - 100 hour week) teaching/grading/counseling, etc..... research, such as it is, is accomplished during the summer/X-Mas break WITHOUT PAY. My wife has a 300K grant, but she does not pay herself a dime out of it during the summer; she spends the money on research assistants, equipment and supplies.
Most (but not all) of her good students go on to Medical School; a few get the disease and go into graduate school (which are filled with Oriental students who get educated, many returning from whence they came). The PI's here like them because they work VERY long hours, for very little money before they earn their degrees. The typical American, even the good ones, have trouble competing; although some do (but not as many as 20 years ago).
Just my 2 cents.