"I do not buy the melting pot / LA thing " You said that based on your one time experience talking to fans at the Saints game.
I DO buy the melting pot thing because I live with it right here in Orange County. In a two block residential area I live close to and have plenty of friends who are Charger, Saints, Patriot, Seattle, etc fans-and when they can afford it they DO go the Coliseum games when their team is in town. I think that is true for two main reasons: 1) they move here without losing their fandom from the area they left; 2) the long duration this area (So Cal) had no professional football and with the rise of the game's popularity people adopted teams.
You do have a point in the original sale of tickets to brokers. That's how I go to most of the games.