I suspect it's not that simple, sure a Samsung 42inch tv and phone cost the same, but they perform very different things. The software on the phone is vastly more expensive to license, create and test compared to the tv. Not to mention the fact that shrinking the components down while ensuring they don't overheat must be an engineering feat on its own. TV's have non of these issues, and the software is much simpler, my old plasma tv probably had less than 256mb of ram.
And of course, if people are willing to pay more for it, then charge more. The mark up on an iphone is like $200, on each phone.
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