Let's face it, the NFL is a extremely lucrative business (thanks to us fans), with so much money being made that teams are able to secure the elite players with guaranteed money. So as long as we all keep watching, buying jerseys, etc the money is there for them to spend.
It's extremely lucrative for the top earning franchises, moderately lucrative for the middle third, and generally a lousy investment for the bottom third.
The Packers, for example, are among the more healthy franchises, ranked 13th. on the Forbes 2014 franchise valuation list. For the 2015 fiscal year, the Packers reported record revenue of $375.7 million and net income of $29.2 million. That's a net margin of 7.8%, which is hardly "extremely lucrative" relative to, say, an average Fortune 500 company. Since they dipped a bit into reserves, it would appear net cash flow was negative. The difference between net income and the negative cash flow would appear to be accounted for by capital investments in the entertainment/lodging/shopping/whatnot complex surrounding the stadium in an effort to increase unshared revenue. It is a speculative investment...as we know, "build it and they will come" is far from a sure bet. And the Packers are hardly unique...unshared revenue is the owners' holy grail.
The NFL's impact is far more a cultural phenomenon than a financial one. Goldman Sachs, an investment bank (actually a "systemically significant" commercial bank with the associated capital requirements, but who's counting) is comparable in that such enterprises have a high number of highly compensated individuals taking home about half the revenue. GS is currently valued at 4x the Forbes' entire NFL valuation which is probably understated based on the Bills sale, on about 3x the NFL's revenue.
The most lucrative franchises are primarily the one's with long term ownership (individuals or families) with a relatively small initial investment...the return on invested capital must be very attractive for them. Their big issue is estate planning.
But what would induce someone like Terry Pegula to pay $1.4 billion cash for the Buffalo Bills, carrying the 31st. highest Forbes valuation of $930 mil with only the Rams ranking lower? And the Rams are demanding a new St. Louis stadium or, better yet, would jump at the chance to make the move to a new stadium in LA.
The answer to the Pegula question is mostly ego, I'd say. He zooms to the top of the list of most recognizable names in the region. He is a local hero for keeping the Bills in Buffalo, surpassing Cuomo (who gets mixed reviews for gun legislation among other things) who has committed $1 billion in Buffalo investment, $200 mil alone going to Solar City for 1,200 good jobs and supplier knock on affects.
Pegula is probably envisioning economies of scale and synergies with his Sabres ownership, but that's hard to see since the two stadiums are nowhere near each other. He did make Brandon president of both the Sabres and Bills, saving a paycheck, so that's something I guess. Long term, he'd have to be envisioning a downtown dome near the hockey arena, mostly on the taxpayer's dime, otherwise it doesn't make much financial sense. That's going to be a tough sell, and makes for a highly speculative investment, not a cash cow.