Honestly, if I was a politician and a billionaire came to me asking for stadium funding, I'd tell him, "Yeah, no problem. What equity stake are you providing in your business for this kind of investment?"
It's plain to see by now that sports franchise ownership is incredibly profitable; it may actually be in the best interests of a city to operate a professional franchise. It's an asset that keeps increasing in value, and knowing it can't leave will be a huge assist to local businesses buying into the neighbourhood (especially if an expansion franchise and new arena were used to develop a brownfield-type area).