How to get iphone cases printed and sell them?

I'm a college student studying graphics and I heard people in my class who have started their own phone case company. I'm interested in also selling my designs and getting them printed onto a case but I was wondering if there was an easier way rather than buying quantities then selling them on ebay. Do you know if there are any websites or companies that can send my designs as soon as it is purchased otherwise I would have to buy designs, then put them up for sale which is a longer process.

For reference there are relatively expensive print on demand services like Zazzle.com, Cagepress.com and customink.com which can print any quantity, their model allows you to upload your art and setup an online store hosted on their site, you typically can choose the markup above a base cost.

A web search should turn up printers who can handle moderate size runs of 50 or so pieces, serious players get it done in China, though you should be educated before dealing with a Chinese supplier like you may find on Alibaba.com

There are promotional gift suppliers who provide wrist bands, coffee mugs, etc with a company name added, many of these do cell phone cases as well, try searching for:

promotional gift cell phone cases

Why do you suppose they are doing it that way? Its because its the easiest and most cost effective