Employee retention has been a huge part of my job for over a decade. In the professional world, employees rarely leave over money.
It's generally about opportunities to do new things/grow in their career (which is distinctly different from compensation), a culture problem (which compensation will not fix), or an engagement problem (poor leadership)
I'm sure your anecdotal experience clearly changes how the science of studying human behavior works.
That's why COVID boosters were so pointless - your cousins brother's friend got sick from the booster so obviously they're full of metals that solidify in your circulatory system.
The only way I can see what he mean making sense is that he's talking about the people making more than low 6 figures. I can totally see someone making 300k a year not leaving because of money but because they wanna do something new.