Cities do have a "union", it's called the city government. Fans (aka people) bargain by electing people that agree with them. So far fans (aka people) are elect

Cities do have a "union", it's called the city government. Fans (aka people) bargain by electing people that agree with them. So far fans (aka people) are electing people who think the cost/benefit of paying for stadiums is a net positive. If so many cities wind up taking a loss on the matter then I suppose things will change.