I see a point: Spend $400 more upfront to avoid having to pay $30/month x 24 months=$720 for a data plan that I can live without.
I guess I just view the iPhone as largely useless without the data plan. I'd just buy an iTouch and a cheap flip phone for a phone then, and then while I'd have to carry a phone and an iTouch, I wouldn't have spent $600 for the convenience of having it in one device.