Tax evasion is not very rare in my country.
Tax evasion is more common than people think, and those who usually blame others for evading taxes, do the exact same thing without realizing, or they are just a bunch of hypocrites and only point at the wrongdoing of others.
The very fact that a large group of people talking about tax evasion and consider it a crime is already quite shocking, because all it technically is, is self protection.... protection against criminals who want to steal your money by force.
Well.. it depends on your ability to hide your evasion. Oligarchs and billionaires have talented CAs out there to help them, and they normally pay much lower taxes rates when compared to the middle class (making use of all the loopholes and tax breaks). What they are doing is entirely legal, even if it is not very ethical. Also, most of the income for the super-rich comes in the form of capital gains, dividend and stock options and there are enough loopholes available for them to make use of.
On the other hand, the middle class gets most of their income in the form of salary. Now the catch is that there are not many loopholes available with the salary income, to qualify for a lower tax rate. So these guys are forced to pay a higher tax rate when compared to the super-rich. This is not fair, but the system works like that. Because if a particular country increases the tax rate for the super-rich, then they'll just migrate to another country, where the tax rate is low. With the middle class, there is no such risk, as they can't afford to shift.