Why don't they just buy their own country?

The Times today has a story about the Wall St. hedge fund managers whose annual incomes are over a billion dollars. What I want to know is how much they pay in taxes? Very little, I'm guessing. How about a new law: Anything over 5 million in annual income goes straight to the government? Maybe it could have a codicil: not to be spent on war, only on domestic services? Could that get some kind of national health care going?