The cheapest corkage fee I've come across was $10... So it's definitely not worth it to bring your own if they've got the same kind of wine at the restaurant. It doesn't come out cheaper to BYO. However, I think it is illegal in California to BYOB at a place that doesn't have a liquor license. The only time it makes sense to bring your own is if you want a particular bottle of wine that the restaurant doesn't have.