Charlotte's already ponied up their ransom money so I'm not sure what your point is there.
Investing into large public work projects have been shown time and again to be financial losers for local governments, so if those cities want the prestige of owning the team they've got to pay the price. You can look at it as a PR expense if you like.
End of the day, what NFL owners are doing is leveraging the local populace's emotional attachment to the team to more or less extort public money. Like Zod said, if there was a little more local emotional attachment to use as leverage, there probably wouldn't be all that much flack from most people on here.
So, Charlotte does not need or want the Panthers in your opinion. And I willing to bet you you didn't read the whole thing, as to why you can't get the point. Though it wouldn't matter, as you have made your mind (no changing that...) up, anyway. Just don't cry about it, if and most likely, when the Panthers decide to leave Charlotte for a city that will.
All big businesses get help from the community (to relocate or even stay) one way or the other (and it almost always is in the form on money).