My game has an income tax. Anybody who makes over 50,000gp/year is in the 50% tax bracket. The governments of the world has joined forces to create an uber-epic device that magically takes their share of taxes as soon as it's earned. Works in anti-magic zones, across planes, etc.
At one point, the party got so bothered paying taxes, they started doing adventures pro bono (ie, for free).
After Obamacare was passed in the US, my fantasy world had a meeting and let people vote on national health care. It would raise the taxes to 60%, or to 75% if it included True Resurrection. My players voted 5-1 in favor of the 75% version. The 1 voted for no national health care. After months of playing, they all now wish they didn't have it (they're about 20th level and easily pay in far more than they get out)
FWIW, the original tax doesn't really matter. I simply gave them twice the wealth I otherwise would, then took back half in taxes. Eg, if WBL says they should get 125,000gp, I gave them 250,000gp, then took back half. Since they voted for national health care, I do not raise the amount the get, so in the above example, they would only get 62,500gp in the end.