NobodyReally
Superstar
How much does it cost to go brehs? And do u have to go in a costume?
I've never been to the San Diego Comic-Con, but I go to the Chicago and New York one regularly. It depends what you want to do, how long you want to be here, and what's available. You can go for a day or for three. You can just go to the main floor and walk, or go to special VIP screenings, comic and art signings, celebrity meet and greet and photo ops. All of the extra costs.
I recommend NOT going in costume your first year, just go and observe. If you want to COS play and do it well, you should see how the pros do it. But no, most people do not go in costume.
Here's more info on the badges and entry fees: Purchase Badges