Who'd benefit from Ubuntu Dell rigs costing $225 more than Windows rigs?

Over on Slashdot I came across an interesting post this morning going by the title of Turns Out Ubuntu Dell Costs $225 More.  It's about how a free RAM and hard drive promotion worth $275 (2GB memory and a 160GB hard drive) actually mean that Ubuntu notebook rigs cost more than equivalent Vista notebooks.  Now the discussion about this particular promotion seems to be a moot point because Dell's pulled the plug on the promotion, but I can't help but wonder whether there's more to this promotion than meets the eye.

OK, it's not news to anyone moving in tech circles that PC prices are very dynamic change all the time, but this one struck me as particularly interesting for a number of reasons.  First off, we have clear proof that Dell will use aggressive promotions to shift Windows PCs but not Ubuntu PCs.  The Dell/Microsoft alliance is still strong (a business move that makes sense).

Secondly, this price drop wasn't a response to fluctuating hardware prices but a temporary special offer on the hardware.  If Dell wanted to shift notebooks, why not apply the promotion across the board?  Why preferentially apply it to Windows rigs?  Who's picking up the tab here?  While many Ubuntu users wouldn't really need 2GB of RAM, the extra hard disk space would have come in handy, and if the RAM's free, why turn it down?  After all, you never know when you might need it. 

Thirdly, dissect this "$275" offer.  No matter how I cut it I can't make difference between two 1GB RAM modules and a 160GB drive compared to two 512MB RAM modules and a 80GB drive come to anything near to $275.  Not even $200.  More like $100.

While it's fun to entertain conspiracy theories that this is a Dell/Microsoft plot to sink Ubuntu, the true is probably far more pedestrian.  Dell's Windows-based notebooks and desktop PCs have to compete and remain competitive with offerings from other vendors.  The Linux rigs, given the small market, do not. 

Thoughts?