Haven't read the whole thread but the problem with looking at only state income tax is that there are other taxes and fees that people pay that differ from state to state.
Example, if you made $1,000,000 a year for the Pittsburgh Penguins, and you lived in Pittsburgh, you'd need to make $1,200,000 for the same cost of living to play for the Panthers (I used Ft. Lauderdale as the comp here). But Florida doesn't have an income tax and Pennsylvania does. If that same player went across the state to Philadelphia, he'd have to make 1,035,000 for the same comp salary.