iPhone 3G will be available for $199 (8GB) and $299 (16GB) for iPhone customers who purchased an iPhone prior to 7/11, customers activating a new line with AT&T and current AT&T customers who are eligible for an upgrade
Existing AT&T customers who are not currently eligible for an upgrade discount can purchase iPhone 3G for $399 for the 8GB model or $499 for the 16GB model. Both options require a new two-year service agreement.
A no-commitment version of the iPhone will be available for $599 and $699; however, this version may not be available on July 11th launch.
Engadget has organized and posted the iPhone plan details as shown below!