I guess there are two main reasons for why they'd charge more for Linux than windows:
1) Higher tech support cost
2) Keep in mind: the purchase price of a new windows machine is often partially subsidized by all the crapware they load on top of it. Those URL assistants, 60-day trial versions of Norton anti virus, trials of Word Perfect and all that other junk aren't pout there out of the goodness of Dell's heart -- they are put there because the companies in question pay them money to do so.
Linux = no 3rd party commercial crapware bundled, meaning they're missing out on that revenue stream... Which can result in the price for a machine with a free OS being more than one with a commercial OS.
1) Higher tech support cost
2) Keep in mind: the purchase price of a new windows machine is often partially subsidized by all the crapware they load on top of it. Those URL assistants, 60-day trial versions of Norton anti virus, trials of Word Perfect and all that other junk aren't pout there out of the goodness of Dell's heart -- they are put there because the companies in question pay them money to do so.
Linux = no 3rd party commercial crapware bundled, meaning they're missing out on that revenue stream... Which can result in the price for a machine with a free OS being more than one with a commercial OS.