I see your point.
Mental and physical work can tire equally.
It has been my experience in life that a skilled worker can and usually does make more per hour than a white collar worker.
It is not unusual for skilled workers to make more, with over time, than maybe his supervisor and probably a degreed white collar worker.
When I was young this was so. I went to a refinery, here in this area, too apply for a job. Was told that they would not hire a degreed person as they thought he would not be satisfied in the long term.
I have a good friend who has a degree from Texas A&M--he is younger than I--and he went too work for Shell. Ended up in the lab and he was making more than me consistantly thru the years.
Now I am not complaining or bemoaning his, or any's, gain--it is what it is. I made, what I consider a good living, better than 70K, and loved the work.
Got fired from that job when I was 52---fired, Hummmm---they called it a layoff---never understood the difference. Anywho, I made out pretty good in real estate, until I was 62---when I quit.
The funny thing about salaried workers and hourly workers is the hours worked. I rarely worked 40 hours a week--it was, more than likely, 60 hours a week---but no overtime. There were advantages ofmy job over that of a hourly worker though.
Blessings