If they want to move, let them. The opportunities for making money would still be present.

There's a bizarre notion going around that protecting the economy requires protecting the rich. However if you look at it, it doesn't make any sense. The strength of an actor in the economic system is directly related to their participation in that system. The rich are where they are because they hoard more of their wealth. Hoarded wealth slows down an economy. The rich are poor economic actors, let them hoard their money elsewhere.

"The opportunities for making money would still be present."

who will take advantage of those opportunities? people who take advantage of opportunities to make money have already moved out, haven't they?

Let's use a hypothetical example. We bring in the wage cap, some wealthy people move elsewhere. Let's say one of the wealthy people ran a profitable supermarket. Are you saying we couldn't find someone who lived in the country to run a supermarket in the same location?

High earners don't even move from New York to New Jersey when New York raises taxes (google it).