Hell, a 40GB Barracuda IV is verging on 2 bucks per gig ($1.75). It gets lower as the size grows of course. Frighteningly, a WD 20GB is 62 dollars, over 3 bucks a gig.
Seagate just doesn't sell as many drives as Western Digital and Maxtor, I'd assume, so they can't cut their prices very low in the first place, and the resellers can't put them on sale easily. The Barracuda is Seagate's ONLY consumer hard drive, as well, so they don't have as much of a product range to have varying prices.
I still don't see any Western Digital drives significantly lower priced. 95 cents per gig is the lowest Newegg has, and that's only one 2MB cache model, all others are over 1 dollar per gig, but not nearly the prices of Seagate's. Their 250GB drive is $1.55 per gig, while Seagate's highest capacity Barracuda V 120GB is only 1.15 per gig. A WD 80GB 2MB cache is only 5 cents per gig cheaper than an 80GB 'cuda IV.
I think it's just that Seagate has such a narrow range of products, combined with the lower sales volume. It's interesting that the very smallest 'cuda drives have such a high per-gig price -- it shows how much they focus on the higher end products, while Western Digital and Maxtor are able to focus on a wider range.
Maxtor's prices are even worse in some cases. Over 2 bucks a gig for a 30GB drive. Buck and a half for a 60GB. But overall they line up well with WD's prices.