700£/month would be an absolutely massive expense in my place, and there's essentially no chance we could afford it. We don't get much draw for sporting events, even the Superbowl or what have you.
That doesn't mean that everyone in the place during the Superbowl doesn't want it on, though.
So although it couldn't possibly pay for itself at my place, not having it would also cost us quite a lot when there are big games.
I can't blame pub owners for wanting to save money wherever they can. But I don't see this as being particularly expensive for the context.