According to BusinessWeek, the real cost of building a Kindle 2 is around $185 but Amazon charges users 48% more, to be exact $359, 

A teardown analysis of the Kindle 2 by market research firm iSuppli estimates the cost to build the device at $185.49, or about 52% of its retail price of $359. ISuppli takes apart consumer electronics to identify the manufacturer’s suppliers and estimate the cost of the device’s components, providing a rough idea of the profit margin for each unit sold. Amazon declined to comment on iSuppli’s analysis.

Via:  BusinessWeek