You're thinking really, really small. In fact you are buying the entire NFL paradigm that teams have to "live within their revenue." No, they don't.
The value of their franchises is constantly increasing. Thus, the share price and value of their stock is constantly going up. A corporation that is this profitable, with their FMV of the company just zooming up every year for 30 straight years, each one more profitable than the last, can do many things to raise revenue, not tied to current year earnings.
It's a simple accounting principle. They can convert a small portion of their equity into private securities transactions or simply borrow money against future earnings or equity position. Lots of ways to structure such transactions.
They don't want to do that, and since they are a monopoly they can force the players to accept contracts that are vastly less than their actual productive worth, when measured against the only measure that matters at all in business - their total stock value of their franchise.
In the case of Pat Bowlen he bought the team in 1984 for $78 million and Forbes Magazine states that the Broncos are worth $2,600,000,000. That's two-billion, six-hundred million dollars for the math challenged among you.
A total increase of over 33 times his original basis. That ladies and gents is what is called "a good investment."