They should make a money substitute system. You take your cash, plus maybe 5%, and take it to a bank. You then exchange the cash, plus the 5% tax, into a cert/bond of some kind. This bond, can then be exchanged for the amount of cash you put into it. If people are so rich, that they need a higher cap, then they shouldn't be too mad of losing 5% of it every time they want to be able to technically have 2.1bil certs/bonds of 2.1bil.