Do you really mean that??? I've looked at several external hard disks for months and a few months ago I finally went for an internal drive and an enclosure. It was a lot cheaper than buying a stock external drive!!! It's been doing pretty well too. Except in a few cases where "branded" external drives could be cheap, buying an internal drive and putting it in an enclosure yourself would save a lot of money!
With "branded" external drives, they charge at the higher end towards a dollar per Gig. For an internal drive + enclosure, the cost of the enclosure right now varies from $25 to $40 depending on what you buy, but the best deals for internal drives come between 30 cents to 50 cents a Gig. So the larger the hard disk you buy, the lesser your per Gig cost if you build it yourself (it's very simple to build it too). Recently CompUSA was (or maybe still is) offering a 160GB HDD with a separate enclosure together for $60 (after mail-in-rebates).