This is why I've always been skeptical of high _income_ tax rates. First tax avoidance is at base a fixed cost. It's the price of a really tax lawyer (or at the extreme a couple of US Senators). If that fixed price is less then your tax bill only idiot pays the tax bill.

The second reason is that I don't believe people view money fractionally - I think they look at it absolutely. For me am million dollars is a lot of money. For Bill Gates though a million dollars is ... a lot of money. It doesn't matter that he's a billionaire he's still not going to throw around a million dollars the same way I'd throw around the same fraction of my wealth that a million is to him. He still recognizes the absolute value of that money and he can still see it's potential to make things happen in the world just as I can see what a hundred dollars (or whatever my fractional equivalent is) can do in the world.