$100,000,000 that's it. At that point we give you a gold "I won capitalism," trophy, and you either retire, and are taxed at 100% of assets above $100,000,000 or, you don't and are taxed at 100% on assets above $100,000,000. This applies to both liquid and non-liquid assets.

Also you can leave your children $5,000,000 in total assets per child over your entire lifetime. The rest of your estate goes into The Sovereign Fund for Humanity's Poor.