Is there an issue of a (halachic) government taxing individuals on the basis of their income?
It is permitted for a halochik government to tax individuals on the basis of their "income" (how much money they own)
(at least in certain cases) (maybe it is becouse it is like tzedoko)
As can be seen from these sources regarding city government
Shulchan aruch harav hilchos Talmud Torah 1.3
PS how much a husband needs to support his wife is also based on how much money he has