Actually, Apple doesn't really market to video editors, graphic designers, etc anymore. The 17" MacBook Pro was bought pretty much exclusively by the three groups you mentioned (I happen to be a developer and I love my 17" MBP) and now they've axed it. The mac-based pro services retailer and consultant business I work at has also heard rumors that this will probably be the last Mac Pro refresh. Anyway the Retina display does NOT provide more screen real-estate. The sole purpose of it is to increase the visual quality of text and graphics rendered onscreen by quadrupling the DPI.
Apple has always been about selling the average joe's computer, right back to the Apple II and the Macintosh. They haven't always done this successfully, notably when Jobs was ousted and Scully nearly drove Apple into the ground by effectively commoditizing Macs. Now they're back on track, what with the success of iPod, iPhone, and iPad. Apple has also refined their portable offerings and made them even more attractive to American middle class students. I personally know six or seven college students that bought a MacBook Pro (most of them 13") from their school because they're hip and they got an education discount.
If anyone's comment is useless, it's your own. I doubt any of us here have any real knowledge on the cost breakdown of the new Pros. (I can, however, tell you that 3rd party Apple retailers have a very very small profit margin on actual Mac hardware. We're forced to make our money on peripherals and upgrades.) So anyone's comments on the pricing of these models are opinions. I happen to agree with GP's opinion on the starting price. You, on the other hand, have no factual basis on which to say that they should probably be $3000+.
As far as building 3 desktops for that money... Personally I've always looked at comparing DIY build prices for PC to notebooks in general to be apples and oranges. Notebook components are more expensive as a rule. Moreover, high-end desktops are significantly cheaper to build than to buy as-is simply because of the way the market works. I happen to have built a fairly well-spec'd Hackintosh for my at-home desktop computing. Not that I don't consider say an iMac to be worth it's price, I just felt I didn't have a need for the design features that make them comparatively expensive (all-in-one form factor, aluminum casing, large screen, etc). On the other hand, I'm quite happy with my decision to buy a 17" MacBook Pro a few years ago. I've gotten a great deal of heavy use out of it and it goes without saying that it's been much more reliable than my Hackintosh.