Heh, yeah I already said the PM article was bullshit. They write for non-nerds. Me? I'm a nerd.

You pointed out that the two computers being compared there were different. Well, the Inspiron and Macbook Pro are also very different!
Anyway, here is a list of the specs that are different to show you that these two computers can't be fairly compared:
Inspiron 1520: $1,394 US
Video: GMA X3100 (shared memory, 2.0 shader)
RAM: 3GB
HD: 320GB
Network: Intel Wireless-N Mini-card, 10/100 ethernet.
Warranty: 3 year In-Home service, phone.
Etc: 2.0 audio out, mini firewire port, fingerprint reader, tray CD drive, card reader, etc etc etc.
Macbook Pro: $2,348
Video: Geforce 8600M GT (256MB discrete, 4.0 shader,)
RAM: 2GB
HD: 200GB
Network: Airport Extreme
Warranty: 3 year limited, phone.
Etc: Magsafe power adaptor, audio/optical in/out ports, FW800, FW400, Expresscard34, Bluetooth, 10/100/1000 ethernet, slot loading CD drive, etc etc etc
So as you can see, the Inspiron and Macbok Pro are different machines. You can't compare them. The MBP has a bunch of extra crap that the Inspiron doesn't have, and vice-versa. The Inspiron is closer to the Macbook, and the XPS is closer to the Macbook Pro. Lo and behold, their prices are much closer too. Why, you ask? Because they have similar hardware!
Go down to your local computer store and check out laptops with similar configurations. You may find that Sony computers have a slightly higher price than Dell machines. Same with Lenovo, Toshiba, Acer, etc etc. They are all companies competing for business, so they will price their products accordingly. Now that Apple is using similar architecture to major PC manufacturers, they are on a level playing field. In order to win over the consumer, a computer company must offer things other companies do not, such as better warranties, faster shipping, different features, different build quality, more options, different extras... The list goes on and on!
PC nerds and Mac nerds are all mostly equal these days, my friend. Only our choice of operating system separates us!