There is a huge amount of taxes that the ultra-wealthy are currently NOT paying. In fact, the vast majority of income taxes are actually paid by the lower and middle classes, because once you hit a certain level of income you have enough money to pay professionals to help you shelter your money and avoid taxes.
For example, Warren Buffet only paid $1.8 million in taxes in 2015, even though his wealth was worth 72 billion at the time. His wealth literally grew 12 billion that year, and he only paid $1.8 million in taxes.
That means he paid only 0.015% in taxes, in terms of wealth growth vs income taxes paid.
Meanwhile, someone earning $100K would have paid around 20% of their income...