If you work at a very high paying job in finance or at a place like Google or FB, I might agree with this. Some people in those groups make a lot and spend a lot (sometimes more than they make).
For people with more modest salaries, I think that this is tragically wrong for fuck you money, but probably right for relatively modest “nest egg” money.
There is a limit to how much a person can gain by cutting, but that same person is essentially uncapped in earning potential.
The easiest way to get fuck you money is to start a business that solves business problems. Knowing sales, business operations, and tech is a relatively easy way to access this market. Not easy overall, but relatively easy compared to other options that lead to fuck you money.