You're getting paid the market rate
from 5 years ago. Due to inflation, this is 99.9% certainly less than market rate today.
You're ignoring the time element.
You hire the $10hr guy when the market rate is $10... and then give him just enough crumbs not to quit. So in a few years when the market rate is $15, he's making maybe $12. See how that works? Obviously many will jump ship, but many won't or can't (e.g. can't afford a gap in pay/insurance coverage).