It's really odd that you don't factor cost of living into your calculator especially since it's used in every other determination of wealth. If I make $250K US in India for example you're generally way better off than $250k US in the Bay area. The ability to move is arbitrage which a lot of people don't have.

Don't get me wrong I actually mostly agree with your point, I say that as a guy literally dying of cancer, but lucky enough to be in the best place in the world to have a chance. It's just that cost of living should factor into any estimation of class status. If you throw that out literally every American has a moral failing, even those living below the poverty line, which isn't a sensible way to look at it. Class needs to be defined as the purchasing power relative to the area that the person is in. Taxation status/rates doesn't need to take that into account.