It's not an effective tax rate, it's an absurd parody of an effective tax rate.

If that $5 of ""income"" is actually capital gains, then it won't be taxed very highly, and adding another 20% is fine. The discussion of 37% + 4.5% + 20% is misdirection.

If that $5 is honest to goodness income, then on average you're also getting $5 of unrealized capital gains, which means you're not paying $2 on $5, you're paying $2 on $10. Or maybe you realize part of the gains and you're paying somewhere between $2 and $3 on $10. A much smaller impact, and that's only if someone in a medium tax bracket with 20x their income in wealth is even affected by the wealth tax at all.