I recently issued my first RFQ to CDNs (ie asked them for quotes). Now, I used to negotiate and provide bandwidth for a living, so I thought I knew what to expect. But, the responses have been shocking.
Frankly, anyone paying more than 50c per GB is a chump. And most of the CDNs are asking $1 at data rates to serve under 100,000 viewers. There's no way you can make money running an internet TV service at this cost, so they're price gouging. Literally destroying the market they operate in. Thankfully, there are a few more pragmatic operators, but the market remains highly unrealistic.
So, buy a server and use Flash progressive download - or just use normal hosting companies who charge an absolute fraction of the cost of a CDN. Certainly until you have 100,000 monthly users. If is gets busy, buy another server. CDNs aren't rocket science and the edge caching ones may well be of little use anyway unless you're doing lots of simultaneous connections to the same video.