you are assuming that building a stadium would be free of transaction costs. The residents of Fenway and the local politicians have prevented past stadium proposals. In fact I imagine the transaction costs of getting anything of that scope done in Boston would be higher than in any other city besides Chicago or New York.

Since the prospect of building a new stadium in the Fenway or other neighborhood in Boston is slim-to-none at the present, the owners have spent their time finding other ways to maximize revenues, e.g. adding seats on the Monster or holding one big-name concert every year.

So in the Sox case, they’re making money off the pent-up demand for tickets: those who can’t or won’t shell out $50+ for a seat still love their team, so they watch NESN (jacking up the price of broadcast rights year to year), buy hats and jerseys (delicious licensing deals), and–because going to a game at Fenway is such a rare treat–evangelize, turning newcomers to Boston and residents elsewhere into Sox fans. Without that pent-up demand to see the Sox in person, a lot of that falls apart.

Therefore the biggest nightmare, assuming demand is somewhat near supply, is if long-talked-about plans to bring a minor league team to Southie are realized. A Southie ballclub would be just as beloved as the Sox, the tickets would be cheaper, and getting to and from the games might even be easier. Then again, it could redouble the area’s obsession with baseball and drive demand even higher.