Dell released a Linux version of its XPS 13 Ultrabook with preliminary ship dates of the second week in December, if ordered today. The Linux XPS 13 is offered as an alternative to the Windows 7 version, and can be substantially more expensive.
Dell currently offers the Windows 7 version (opens in new tab) of the XPS 13 with base prices from $800 to $1450, with the main difference being between lower-end and higher end versions a 128 GB and 256 GB SSD, as well as a step up in CPUs with the choice being a 1.6 GHz i5-2467M CPU or a 1.7 GHz i7-2637M version. The flagship model gets the faster processor as well as a 256 GB SSD, 4 GB memory, as well as Windows 7 Home Premium.
There are also two Windows 8 models (opens in new tab), one with a i5-3317U CPU, a 128 GB SSD and 4 GB memory for $1,100, as well as an upgraded version with an i7-3517U chip, a 128 GB SSD and 8 GB memory for $1,200. There is no option to upgrade the Windows 8 version to a 256 GB SSD.
At the time of this writing the Ultrabook with Ubuntu 12.04, which originally had been announced as Project Sputnik, was offered for a base price of $1,449 (opens in new tab). The Ultrabook comes with 8 GB memory and a i7-3517U. There is no direct price comparison as Dell does not offer other variants. The Linux version therefore comes at a $250 premium, even if it buys you the larger SSD. And if you can live with the slower processor and less memory, the price difference grows to $350.
Of course, Dell is not fishing for the same type of customer with the Windows and the Linux Ultrabook. While the Windows 8 Ultrabook is a device designed for consumers, the Linux model is marketed as the "ultimate developer notebook".