The 16GB model would generally cost $649, but those who are eligible for the upgrade can get the same device by paying just $199 with a 2 year contract. The iPhone 4S will be available in the U.S. through the three major carriers AT&T, Verizon and Sprint.
This contract allows you to purchase a new phone at the subsidized price every 18-24 months. If you want to find out if you qualify for the subsidized price on a new iPhone 4S head over here and select between AT&T and Verizon.