[spiralx]

But that already happens with property taxes - just look at all the people in California who can only afford to live where they do because their property taxes are fixed at their original rate, and so they cannot afford to move anywhere else within the same area.

[astrange]

The best approach there isn't to lower taxes (although a deduction for a primary household is fine of course) but to allow them to defer payment until it's sold/they die. Since in this situation their house is also worth several million dollars.

[spiralx]

Which then significantly exacerbates the potential for a negative equity trap, because moving now requires paying all of those deferred taxes. So the longer you've lived somewhere the more you need to down-value when you move...