Here is how it works in Canada, I dont much about the states.
You have to get in a 3 year contract, thats like $40 a month, + about $80 to fix the plan and get your sim card fixed and iphone activated. You pay $200 to get the iphone. And you pay another $30 a month for the 'data plan' which is stupid.
So you get stuck in a plan, pay about $70 a month for the regular bill + data plan (more if you use your minutes or in better plans then 250mins a month).
I heard in the states you pay only once for the data plan. And we have only one phone company that sells iphones so no options there.