I've lived outside LA in the rolling hills of Ventura County. I've been to see the Rams and Raiders at the Coliseum and then Rams at Anaheim Stadium. Always plenty of seats available and a generally blase' crowd once you peeled back the hardcore layer. I also remember when the Seahawks tried to move their franchise to LA, already relocating their administrative office before the league intervened to prevent them. Also remember when Al Davis extorted $6million good faith money from the eastern city of Irwindale supposedly to build a stadium on one of their razed rock quarries. What a scumbag crook he was! I've been to Kings games when they they signed Gretzky and you couldn't get a seat at face value, and then after he was gone when you could pick up a couple from scalpers at less than face value.
The LA Metro area is a huge market, pretty affluent including the surrounding burbs so on paper it's a good market. However they are largely fair-weather fans and those who aren't have been emotionally involved in other teams for so long, it's not likely they'll quickly shift their allegiances. Long way of saying, they will back a team that's a novelty - for awhile, or a winner, but unless the game's not televised locally, the LA/Orange County market is far from a license to print money.