Earlier quoted context omitted.
Must be more to it than that. If it was possible to get a good tablet (of any size) to consumers cheaper than Apple, someone would have. Maybe this project started out with your assumptions and ended up with (possibly unsellable) $800 device.
AFAIK, Apple's supply chain is not only legendary, but they'll commit huge amounts of capital to new hardware products in advance. This allows them to more or less own the output of a given supplier's factory, forcing other companies to pay spot prices for their follow-on products.
But, iphones have been out for a while. Long enough for new factories to be set up, old factories to increase capacity, contracts to run out... Should be long enough for things to catch up. Why are iphone's best competitors still about the same price or more?