It appears that http://www.isuppli.com/ does this sort of thing for a living.
They just may know what they are talking about.
A phrase comes to mind:
"They know the price of everything and the value of nothing"
You can price out component costs all you want, but you can not determine profit on those factors alone. I know the register likes to be cheeky, but claiming $100+ profit based on the cost of a materials list is just irresponsible.