I think the cost difference thing has been debunked several times the last couple of years.
Dell Notebook priced at $1099:
Intel® Core™ 2 Duo T5750 (2.0GHz/667Mhz FSB/2MB cache)
Widescreen 17.0 inch display (1920 x 1200)
CD / DVD writer (DVD+/-RW Drive)
3GB Shared Dual Channel DDR2 at 667MHz
320GB1 SATA Hard Drive (5400RPM)
128MB NVIDIA® GeForce® 8400M GS
High Definition Audio 2.0
Dell Wireless 1395 802.11g Mini Card
56Whr Lithium Ion Battery (6 cell)
Mac Notebook priced at $1099:
2.1GHz Intel Core 2 Duo
1GB memory
120GB SATA hard drive @ 5400RPM
Combo Drive (DVD-ROM/CD-RW)
Both as listed on the store's website. A lot less technical information available listed for the Mac.