$300.00 USD is only for the parts (hardware + OS) . I am not counting labor + shipping (logistics cost) + tech support ( 1 year warranty) . Apple charges for shipping seperately anyway unless they are doing free shipping .I am not sure on the labor end, i know about FoxConn the Chinese supplier for Apple pays its employees little under $300/ month (about $258 to be exact) for their work. Their cost may have gone up after a recent strike and i am not sure about the latest numbers. I have heard in some parts of Beijing labor rates have gone as high as $3/hr.
The other guys in the business Kindle Fire, Nook, etc who are selling at $200 are selling at a loss and are trying to make money by selling apps, books and other miscellaneous stuff.
I believe the price was quoted by an Apple spokesman, and was mentioned on CNN after Apple became the world's largest tech company. I dont have a source to post directly on the forum