It is impossible to avoid this tax so no more stories of Warren Buffet's secretary paying more taxes than he does.
Warren Buffet's tax rate is incredibly low is because the majority of his money is in the form of investments. Stocks are little pieces of paper that say you own a certain percentage of a company, so basically Warren Buffet has part ownership of many different companies. Companies are only taxed when they make money.
If his 10 billion dollars just sits there and does nothing, he pays no tax on it because it didn't earn anything. If it grows in value, he still doesn't pay any tax on it unless he sells it or it pays a dividend. This is similar to the way your house gains value but you don't immediately pay a lump sum of tax. You only pay the tax when someone buys it from you. At that point your investment (primary house, secondary house, or stock) is income and can be taxed as a type of income depending on what it is.
Also, the reason we don't have VAT as a replacement for income tax is because it would make selling things a complete nightmare. You put your item on craigslist, guy pays you the money, you fill out your government tax forms.
You might be laughing, thinking "we already have sales tax in my state and they don't do that!" That's because we don't have a large black market for tax-free goods. If the sales tax was 30% then the government would care quite a bit about you selling stuff on craiglist and not claiming it on your taxes. It would go in the same category as getting paid under the table to avoid income tax.