I do income taxes and this conversation is far more nuanced than the Cap Friendly calculator.
First of all. Last I checked, Brooklyn is part of New York City. While the Islanders do pay NYC tax on Brooklyn game days, they do not pay it on most days because all of the players live and practice on Long Island.
Westchester is not however part of NYC and when the Rangers work at their practice facility and if they live outside of The City, that can be reasonably excluded as a non NYC work day. Tax experts look for every last loophole like this.
There is a mechanism under Canadian tax law where players who do not live in Canada year round can significantly reduce their taxes. I am not familiar enough to fully explain the law but agents and tax experts know how to structure contracts accordingly.
And finally, the cap on deductibility of state taxes on federal incime will become a huge issue starting with tax year 2018. It will create an even bigger disparity.
The bottom line though is that the tax issue is very relevant, the problem is getting bigger due to the federal tax law changes and the teams need to petition the league to address this disparity when the next negotiation with the players happens.
How do the NHL and NHLPA deal with this issue? It's too complex.