taobao.com has lots of postings for cases at cheaper prices. (though I can't vouch for the quality, some basic cases have cute designs on them and are cheap!) if you are not literate in Chinese, there are some taobao clients.
the downside is it's located in China and overseas shipping is very costly, which defeats the purpose of its low price for me. however, if you can get it shipped to a location inside of China and then have a friend bring it to you (or maybe you live there) it's not bad.