Don’t understand how Tampa has been able to use their “tax haven” status so well in previous year. Whereas teams like Toronto where yes the tax rate is high but the endorsement incentive could easily offset that.
Guys at this range is where the tax haven status is most crucial. Deals like this can't really be paid out in signing bonus, so players have no choice really where they pay taxes, so the difference between Florida and Toronto becomes more apparent. Also, I don't think players signing for less than $1M are really being swayed by endorsement money. Back to back stanley cups has more appeal than anything, so best shot at being a repeat cup winner on a low tax state team, very reasonable decision to sign in Tampa.
In the end though, this signing likely gets a bit blown out of proportion because he played on a team that won the cup last year. He is a good player, and this is a very good depth signing, but does it really move the needle more than signings like Brassard, Spezza, Nichuchkin? Likely not. I would say Shattenkirk, even if it's nearly double the AAV, will have a better chance to make a significant impact, just because Tampa's right side D was thinner than their forward group, so the opportunity to make a real difference will be greater.
None of this is to say it's not a good signing, but these types of signings, low risk, low AAV that can be buried, are typically going to provide the best bang for the buck because they are found money.