About a 2 months ago I saw an Xbox 360 HD cable in PC world at 29.99. At this point I had already ordered an xbox. I was going to buy it, but then I thought to look online first, just aswell! I found a good quality, branded cable on Amazon for 2.99, the only reason it was so cheap was that it was not official Xbox 360 stuff. The same story goes for the wireless connectors needed for Xbox Live. Xbox 360 connector - 54.99 , belkin gaming connector - 29.99. Similiar stories for the headsets, keyboards etc.

hope this helps!!!