And it doesn't hurt that he can get special deals that most people can't.
http://www.slate.com/articles/business/moneybox/2011/08/no_y...
On the Bank Of America deal.
This isn't an ordinary investment, in which an investor buys common stock. Buffett's $5 billion is buying him 50,000 shares of a special class of so-called "preferred stock," which will pay him a 6 percent dividend, or $300 million a year. Just for the sake of comparison, BofA's common shareholders get a quarterly dividend of one penny a share. That means that if you owned $5 billion of ordinary BofA common stock at its current price of about $8 a share, you'd be getting a paltry $25 million a year in dividends—less than one-tenth of what Buffett will get. (Earlier this year, BofA tried and failed to get permission from the Federal Reserve to increase the dividend.)
BofA can buy back Buffett's investment at any time for a 5 percent premium.