Well, for starters the main difference between Mets and Coyotes would be the lease. The Mets came with the lease to the ballpark on absolutely sweetheart terms. The baseball-loving Mayor gave his beloved Yankees everything they wanted... and a matching deal to the Mets, on his way out the door when his term was expiring.
There's no "dealing with Glendale" component of the Mets.
Secondly, the Islanders TV contract isn't based on their WORTH as a broadcast asset and the fans who watch.
SportsChannel was a pioneer in "sports on cable" and signed the dynasty-era Islanders. The deal gave the Islanders the option of renewal for X dollars OR take an ownership stake in the company.
Cablevision bought SportsChannel before the Islanders deal was up. So James Dolan had to buy out that clause in the contract. He wasn't giving the Islanders an ownership stake in Cablevision (which includes MSG, MSG Network, the Rangers/Knicks, etc).
And the Islanders owner at the time, was John Spano, a crook who needed money fast. So he cut a deal. The Islanders got FIVE TIMES the market rate on a 25-year contract that saved the team from relocating when they had 15 years to go on their horrible lease.