Aluminum is a good material, but it doesnt change the fact that macs have about $500 worth of hardware and a $50 OS and the computer costs $3000. Where does that other $2450 go? (Im talking in US dollars btw)
You can custom build a PC for $1000 with much better specs that will last just as long as a mac, and if you like Mac OS, you can put it on a PC. Its the fact that their hardware is so shiny that gets the sales.
And the new nano has multitouch. The only thing you can really do with the multitouch is rotate the screen by twisting 2 fingers on it. But why? Do you really need to be able to do that? Its an MP3 player. Stuff like a multitouch screen on an iPod that small just wastes memory and uses up storage space, since it isnt really useful for anything.
If you custom build, it will be cheaper than even major PC manufacturers, for the same hardware.
It depends where you live, though. Where I live in Canada, the last time I calculated for parts, I ended up with the double of the original price I would have paid for a pre-built computer