> That excludes all fans who don't live in big cities. A lot of people travel just to go to shows.

Not really. The place that sells the tickets doesn't have to be the performance venue itself.

This sort of distribution was quite common pre-Internet. In theory it's even easier now, because so many of the venues have (unfortunately) consolidated under vertically integrated ownership (e.g. directly owned by Live Nation). Which incidentally, after scalping, is the biggest reason that ticket prices are so high in the first place.