Apple's 16GB iPhone 4S carries a build of materials (BOM) of $188 before factoring in manufacturing costs. The analysis was performed by iSuppli, one of several teardown specialists that conduct such work in order to estimate build costs and identify hardware vendors that supply parts for various consumer electronics.
Aside from memory capacity, the two other iPhone 4S models are identical internally. The 32GB handset has a BOM of $207 while the 64GB phone has a value of $245. As you can likely surmise from the overall costs, NAND flash is one of the most expensive components inside an iPhone.
16GB NAND costs $19.20 in contrast to a 64GB setup which is $76.80. The electrical system is the next most expensive subsystem at $33, followed by wireless capabilities at $23.54 and the display at $23.
Surprisingly enough, items that most would expect to be very expensive are relatively cheap. The A5 processor and camera subsystem, for example, are only $15 and $17.60, respectively. Sensors and user interface components only total $6.58 per phone.
iSuppli points out that their analysis is preliminary in nature and only accounts for hardware costs. Other expenses like software, licensing and royalties are not included. Manufacturing costs are listed at $8 per handset, regardless of capacity.
Carriers offer the iPhone 4S at subsidized prices of $199 for the 16GB model, $299 for the 32GB unit and $399 for the 64GB smartphone with a two year service agreement. Apple sells each phone to carriers for much more than this but service providers eventually make back their money and then some over the course of the contract.
Photos courtesy iFixit.