I can't tell if you're being serious - but when people start moving out because of excessive taxation, prices drop and tax revenues go down with them (because real estate taxes are based on home values).

Capital flight lowers real estate tax revenues. This should be obvious, so maybe your comment was a joke?

FWIW, in NY generally the tax assessed value of properties is far below the market price (20-30%, sometimes more).

NY could afford for the "market price" to fall quite considerably before it would significantly affect tax revenues.