You forgot the casing and the power supply.
And the special sized (small) motherboards come at a large premium;
mini-ITX board (17x17cm) here cost about 200-250! ($300-350), deff not the standard micro-ATX (24.4x24.4cm)
you mention.
That is nonsense. Apple custom designs and outsources the production for their own logic boards on every computer they manufacture anyway so there is no true retail market value of such a board. Besides, of all the mini ITX boards on NewEgg, the most expensive one was still Under $200. So there's amlost no way a home-built board by Apple would cost more than $100, since it only has to support a limited hardware set, unlike most boards out on the market.
Casing costs pittance to produce. It's thin aluminium mounted inside plastic, mounted in an aluminium sleeve. I guarantee you it costs no more than $10 to produce the case.
The thing I want to know is why all you pundits are so willing to stick up for Apple's shortcommings! Should we not want Apple to strive for more? If there are so many of you out there who keep defending the Mini saying, "oh it's good enough" Apple will hear you and do as it has done... neglected it until its statistics are laughable (and they are). Come on. Tell me that an 80GB HDD and combo drive isn't laugable. I wouldn't pay $300 for a computer like that, let alone twice that, and you shouldn't either. Stand up against Apple for once and tell them that you want to see a powerful yet compact MacMini like they used to deliver, not an OBVIOUS bottom-of-the-rung stock-room clearing over-priced joke.
-Clive