The real metric isn't total cash, it's outgoings vs income.

Billionaires do not have significant non-discretionary outgoings. At the billionaire level food, housing, and transport are essentially free, and your time is your own. There may be mild chagrin if you can't afford a bigger yacht or another private jet, but mild chagrin is all.

That's not true for most people. The poorer you get, the more aggressively you have to sell your time, and the more likely it is that your outgoings are going to exceed your income.

Not because you can't organise your finances, but because inflation and wage stagnation have made any other outcome impossible.