Re: @AC 16:25GMT - Quit your whining
RTFA yourselves. You clearly missed the part where it points out that Dell spent some of their own money getting the drivers working properly for Ubuntu.
THAT is why there's a (rather small) premium. This means Dell had to do work themselves that they normally would not have to bother with. With Windows 7, the component manufacturers themselves do 99.9% of the heavy lifting when it comes to drivers. All Dell's monkeys have to do is bolt it all together properly, test it actually works, then shovel it all into a plastic case with a shit screen.
For the Ubuntu Edition of their laptop, Dell's own people have had to do some of that work, because there's nobody else do to it for them. They've had to muck about with source code and driver support in Ubuntu to make it talk civilly with their choice of components. Only when all the features listed on the side of the box are actually usable can they then shovel it all into that plastic case with the shit screen.
Las time I checked, programmers capable of working on drivers weren't cheap, regardless of the operating system. Neither are project managers familiar with such GNU / Linux projects. So Dell do have to pay for the skunkworks people's time and effort somehow.
Furthermore: providing customer support is a legal obligation in most territories. It's also expensive. Even more so when you consider that most call-centre operators have been dealing with Windows users rather more often than Ubuntu users. That means training will be needed to ensure suitable operators are available for these Ubuntu-burdened laptops.
What happens if a customer decides to upgrade Ubuntu "Anthropomorphic Axolotl" to its next version, which might even have a radically different GUI (again)? Dell need to consider that support aspect too.
Hence the extra $50.
Sounds pretty reasonable to me.