I have not seen an analysis of the costs for ebook readers this year. From last year, see
Amazon’s Kindle 2 Costs $185.49 to Build, iSuppli Teardown Reveals. More than half this cost was in the 6" EInk screen, at $60, and the Wireless module at $40. I assume both are now cheaper in the latest devices. Actually, I doubt that Amazon was paying $60 for the screen last year - given the number they were buying.
iSuppli also seems to have teardowns for the Kindle 3 and Kobo eReader, but they have not issued any public info about them.