What tax revenue drops? Before the change they weren’t paying the additional tax, and now they aren’t paying it if they leave, so nothing is lost on that account. The state loses whatever taxes they were paying originally; given that they’re annoyed enough to leave over an increase that suggests that they were already finding ways to minimize their tax payments. Thus, by them leaving, the state is likely losing a small amount of revenue. Given that each person has a cost to the state, the net effect will be even smaller.
Surely there’s a point at which taxes drive away enough people that it doesn’t work, but it’s clearly not the case for this particular implementation.