Staples.com has their 100-pack of slim (5mm) CD/DVD cases on sale for $9.99. These are Staples brand and they are good quality (I've used a lot of them). The pack is 50 black and 50 colored (clear front, the back is black/colored). It looks like the limit is 10 at this price, and additional ones are $14.99.
The deal appears to be for delivery only; I checked in a store today and the register showed their usual price of $34.99. If you are a Staples Premier member you get free shipping; otherwise you can ship to a Staples store for pickup for free.
The item # is 478455; here's a link: http://www.staples.com/Staples-5mm-Slim-Jewel-Cases-100-Pack/product-nr_478455. (If the link doesn't work then search by the item number.)