At the pre TGS 2006 press-conference of Microsoft in Japan, the company revealed the pricing and shipping date for the Xbox 360 HD DVD drive in Japan.

The Xbox 360 HD-DVD drive will be available starting November 22nd at a price of 20,790 yen including tax (~$177).
There where some rumors about 2 weeks ago from the UK that the price for the HD DVD there would be 199 GBP (~$371). Also part of the rumor was that there will be a Xbox 360 premium HD DVD bundle.
There is still no word on when and for how much the Xbox 360 HD DVD drive will be available in the United States. Possibly next week at the X06 event in Barcelona, Microsoft will reveal these details.
More details about the Microsoft press-conference can be found in the transcripts on Kotaku and Gamespot.