Scientist != engineer; the parent to whom your replying is just talking about scientists as is the mostly good essay he links to (the author is quite wrong about this state of affairs "just happening", but maybe he wasn't looking at the situation in the '80s when the NSF (most particularly) started the big campaign for cheap scientific labor).
I don't know about heavy equipment operators, but I know a welder without any sort of college education who easily clears 6 figures a year. If you know how to weld under water you can apparently make even more.