Yes, people really do "go Galt"...

From New Jersey (BusinessInsider):

Tepper, the founder of the hedge fund Appaloosa Management, moved to Florida last fall. This, according to Bloomberg, has leaders of his former state very concerned. [...]

New Jersey relies on personal income taxes for about 40 percent of its revenue, and less than 1 percent of taxpayers contribute about a third of those collections, according to the legislative services office. A one percent forecasting error in the income-tax estimate can mean a $140 million gap, Haines said.

And Minnesota (TCB):

During the last two years, Minnesota lost or began losing an estimated $2.1 billion in taxable income from 3,099 taxpayers, according to a research study on wealth migration conducted by Twin Cities Business with help from research firm The Morris Leatherman Company (see “The Research” at the bottom of this page). These same individuals have $17 billion in median net worth and $31 billion in median gross estate value.

In almost three-quarters of those moves, respondents said the reason for leaving had to do with Minnesota’s tax policy and collection practices. This amounts to an estimated loss of approximately $1.5 billion in annual taxable income, $12 billion in average net worth and $22 billion in gross estate value due to Minnesota’s tax and collection activities.

The TCB study also found this trend will continue for at least the next five years, during which time an estimated 12,172 Minnesotans will leave, taking with them a combined $5.2 billion in taxable income, $65 billion in net worth and $122 billion in gross estate value.