I can't say how much such a person should pay in taxes, but it is kinda funny that I'm paying the same amount 39.5-40% with my five digit salary and no property.
I don't know who should pay what amount, but I'm pretty sure that me and that millionaire should have different tax brackets. Let alone people with tens, hundreds of millions or more.
PS: I'm in EU, not USA, but here I'm in a highest tax bracket so the point still stands, my tax rate is the same as for any local millionaire. Maybe even more, since those people are aggressively utilizing tax loopholes, shell corporations and offshore tax havens.
You pay the same proportion, not the same amount. 40% of 1M is 10x more than 40% of 100k.
Disregarding all technicalities about what proportion people actually end up paying after performing clever tax planning.
Why are you sure that someone earning 1M should have higher proportion of their income taken away than someone earning 100k?
At some sufficiently low level of income I think it stops making sense collecting taxes, but beyond that I'm not so sure from a fairness-perspeective.
I could perhaps get on board with a hard cap on wealth, for preserving democracy. It is dangerous to have single individuals and families attain too much power. But up to that cap, I don't see any inherent unfairness or inefficiency in that people of moderate to high wealth pay the same proportional rate.