I have a bit of experience in this area. What they are essentially saying is that the Packers bring and leave (and multiply through the spending cycle) that much per capita to the Green Bay Area. This probably includes TV Money, and shared Mdse revenues. Their denominator may be too small, since Green Bay is essentially the State of Wisconsin's NFL franchise, less a few Bear fans in the southern Wisconsin bedroom communities of Chicago. If they are only using the Green bay SMSA, then the denominator is skewing the result.
Ralph has a pretty sweet deal, the taxpayers are on the hook for most of his physical plant, and he doesn't live in Buffalo, so any money he takes out doesn't stay in WNY.
In addition I wouldn't be surprised if Central Ontario, all the way to the Toronto Metro area is included in the denominator, which adds millions of people to our market size, yet we don't see a lot of dollar benefit from that population.
Dallas has huge merchandising and corporate box rentals, and San Diego is the only So. California NFL team, so they benefit from that.
These economic impact studies are all subjective, and depend a lot on how you define the market, what multipliers you select, and what you include and don't include.