Ok, like the $1 Flip Flop sale, I am sure this is going to be chaos. BUT… If you need a Toddler or Infant costume it certainly is a way to save money (maybe not time or sanity!)
Today Only, 10/23/13, $5 Toddler and Infant Costumes at Old Navy (in store only)! Sizes up to 5T
You might want to check out what they look like before going. See their costume selection here.