I guess the argument against this is that some super-rich don't spent on th emainland or not even at all, just bank a tonne of cash. In that case, the overall

I guess the argument against this is that some super-rich don't spent on th emainland or not even at all, just bank a tonne of cash. In that case, the overall income from tax would be lower than it is now. I don't necessarily agree but the idea is normally that "rich" people should pay a higher percentage of their income as tax because "they can afford it". I personally like the idea of a fixed rate from 0 to infinity like Russia iirc, which gives everyone skin in the game and avoids some of the tax avoidance that we see to avoid the thresholds.