I agree that my math is incomplete with regards to what @Peterk2011 has noted in his reply. Respectfully, I would like to reply to your comment, without coming off as argumentative.
Point #1. In the example I provided, the player was given the same offer ($20M over 3 years) and could choose between Indy, Florida, and Texas. I went as far as to say that the property prices were triple the cost in Florida and Texas and then calculated the property taxes and the player still came out ahead by $570K in Florida and 480K in Texas, (all over the three year contract). If we take into account that he player would be taxed differently for home games and away games, we can cut these figures in half ($285K for Florida and $240K). So, does the difference in cost for things like license plates, driver licenses, higher taxes on utilities and higher gas taxes equate to either $285K or $240K over 3 years? Of course not. It's a marginal difference. If we were comparing Indy to California (Bay Area - where I live or NY) you would have a better case. But between states like Texas and Florida, there isn't much of a difference in the cost of living.
Point #2. Please elaborate further, if you'd like. A player in Tampa FL would have no income tax and roughly the same property taxes. A player making $3M in Indy will pay $99,000 in taxes annually, which in my opinion, will more than offset the supposed higher cost of living in Florida for things like license plates, driver licenses, higher taxes on utilities and higher gas taxes. ($99K is more than most peoples annual salary, so there is no way that the difference in cost of living is greater than people's salaries). As far as comparable living situations, there are plenty of real estate comps. Here is an example:
These guys are professional athletes. They will have finance guys look into this stuff for them. It's no coincidence that the argument for income tax comes up when a player is offered multiple contracts from different teams. It's because it is a legitimate concern for athletes making this kind of money. For the average persons salary, it doesn't make that much of a difference. But when you are talking taxes for 20, 30, or 40+ million, it absolutely does.