If you try to buy a new costume early in the season you could be looking at a price tag of 50 bucks or more. There are places that rent costumes but you are better off buying your own because the prices are about the same (and you get to keep what you've paid for). Thrift stores often carry used costmes for a fraction of the price, and you can always try EBAY to find costumes that people are looking to get rid of.