Don't forget the Kindle's wireless hardware. The FCC pics show an Anydata DTEVDUAL module, which is based off of a Qualcomm MSM6500 chipset. An iSuppli teardown of the Motorola Q from 2006 gives an estimate of $14 for the MSM6500 chipset, so that could be a conservative ballpark figure for the module cost, assuming price decreases on the chipset due to manufacturing improvements over the year.
Wow. An e-ink screen has an estimated cost of $200? Wow.
http://mykindle.com/files/kindle_fcc.pdf
http://www.anydata.com/modems.php
http://www.isuppli.com/marketwatch/default.asp?id=351