Or you could, you know, read the article. The directly address why the windows version costs $100 more than the Xbox version, and after reading the entire article, I think it is both justified and reasonable. While I have little expectation that you are going to read this reply, given that I use words, like the article, I am going to summarize the important parts with regards to your statement.
The Kinect for Xbox was subsidized by Live subscriptions and game sales, with the PC version they are going to focus on the hardware and allow people to innovate with their hardware for free. Instead of paying for licenses to develop or for support, etc - you pay the entire cost at purchase, and you will get support for the product without expense.
While you can complain and gripe about the extra hundred dollars, I would implore you to maybe stop and think about what you are getting for the price. Why don't we ask around and see how much other companies are charging for a single device that includes video and audio functionality as well as speech to text translation and motion capture. At $250 this device is a steal. Yeah, times are tough, money isn't raining from the skies, but with all the iMorons blowing through apple products like a new york heroin addict in the hills of Afghanistan, well, skip an update on your phone one month.
I believe that the Kinect is going to do more to revolutionize computer interaction, gaming and functionality more than any invention since the second button on a mouse. They could price this at 500 dollars and I'd put down money that every retailer would blow through their inventory. At 250 dollars, not only will they put one on every computer inside of 2 and a half years, but they are laying down a foundation for young engineers, scientists, hackers and hobbyists to create a community with vast potential.
While this site often condemns the 'greed' of corporations such as MS, Sony, Google, etc - I think this is a case where I feel proud to have put my money towards innovation.