Originally posted by LikeASong:[..]
eBay. My mother, uncle and cousins have iPhone 4s and they got all their cases from eBay. They might not be the most solid stuff ever built, but for 3$ you can use it, break it, and replace it once a month if you wish
I only ever buy cheap ones too (local markets are great for "same-same" goods). I'm really hard on phone cases and tend to break even the really expensive ones.