We could impose a wealth tax that might tax someone like Warren Buffett at twice his actual income and still have little effect on behavior. Mainly because in the US we do not tax unrealized capital gains. Suppose Warren Buffett earns $3 million in taxable income, and his stock holdings increase by $3 billion. If we taxed him $6 million, would he sell his stock holdings? Most likely not. Not saying the idea is prudent though.
On the other hand, if you want a fancy house in France, you can get a nice deal now. Real estate in France is particularly attractive now to the non-Frenchmen.