There is a sticky in the Sarlac Pit section that has a pretty detailed answer for you there. There is no such thing as a 501st approved costume ( for any character ) out of the box, Even if you buy one that is currently approved, it doesn't mean it will be approved for the new buyer ( due to fit , finish, age of costume etc). Price for a completed suit will vary on accuracy, quality, how much you want to do yourself and how many original type parts you want to use. Most complete kits seem to go for $4500 - $7k here for a private sale and I would think it would be a bit more if you had one of the few vendors that offer complete suits do one and you will have to wait a fair amount of time. Piece it together and do some stuff yourself and you may be able to do it for a bit less.