The article isn't about income taxes. Income taxes are taxes on income that you earn in any calendar year.
The article is about wealth taxes. In addition to income taxes, Norway has a wealth tax, which taxes net wealth above $170k (NOK 1.7M) at 1% [0]. So, if your net wealth is $200k, you are taxed 1% on $30k every year.
Separately, it is a myth that the wealthy don't pay taxes. This isn't Reddit. Wealthy pay taxes but they also maximize the value of any benefits already included in the tax code. AMT is an attempt to fix this but has its own problems.