American billionaires, slightly over 8 trillion total dollars, 20 percent, that's about 1.6 trillion the first year, US tax revenue about 5 trillion.

Also almost all the billionaires are gone in a few years, which is fine on its own but we still need taxes from somewhere.

Taxing the billionaires fairly, while necessary for a whole lot of reasons, will not in fact pay for everything that needs paying for. If you want to have a functional health care system, infrastructure, and all of the Good Things, you also need to tax the non-billionaires.