Not official data, but I can say Red Bull Arena was pretty packed compared to most of their games (aka any game not against NYCFC) when they played Chicago, mostly due to a ton of Schweinsteiger fans coming through. Ton of Schweinsteiger DFB and Bayern kits walking around the stadium. Now, I've also seen images of a half empty stadium that's "sold out" so I don't think looking at actual ticket sales for legitimate data will do anything. But, I'm under the impression that a big name can help some way in bringing outside fans to a game.