you can grab a belkin USB adapter(retail) for around $45. Now im going to take a big guess here and say the margin on that like standard goods would be around 15-20% so wholesale cost would be $30 and manufacturing around $20 tops. Which isnt a huge price for M$ especially if each 360 came with it. Mass manufacturing would probably bring it down to $15 ..
M$ charging 80 bucks is a ripoff though.. The 360 is cheap out of the box but not so much in the long run...
Wow, I have had a 360 since launch and I didn't realize I was missing out by not buying a wireless router.