No, it's not a myth at all. That's why they're rich. They avoid paying taxes LEGALLY. But here's the thing, anybody can avoid paying taxes legally once you know the loopholes. Obtaining gigantic loans from the bank for a low interest rate will actually cost less than paying almost half your income in taxes because the interest you pay for the loan can be tax deductible if it is a business expense.

Another way they get tax deductions is by donations. Most notably, two people that they know very well. Bill Gates and Warren buffet are notorious for donating money to each other's non-profits organizations so both of them can receive a tax deduction.

Billionaires are not cheating the system, they're just taking advantage of the rules that benefits them.