I assume there are real inertia issues with moving, probably where with step functions at certain levels of wealth.

Moving at all has inertia, moving to a new city in the same country has a lot more but I suspect moving internationally has the greatest. And the Swiss are a rarity in that they are one of few countries where native speakers can go to nearby countries and still be (mostly) understood.

So it's worth discounting the "if we raise taxes they will all leave" theory for my money