Galley Hero Steve Czaban says yes! I think he may be right.
But the bubble isn't the classic one you might think--bubbles are, in the strictest economic sense, formed by speculators and pro-sports doesn't have a lot of those. There are a pretty small number of owners who are all in it for the relatively long-haul.
Instead Czabe thinks, and I agree, that the bubble may be on the demand side for both tickets and stadiums. If there is a bubble there, then the stadium-revenue model for pro-sports, which undergirds every league, could be in for a big correction.
11 hours ago