How much will an iphone 4 cost me total?

I'm currently a verizon wireless customer, however, my contract does not expire until next year. As of right now I only have the standard $10/month data plan for texting. I'm looking to upgrade this fall before going to college and would like to know the total cost of purchasing the iphone and the cost of the data plan. And yes I've seen/heard rumors of the purported "iphone 5" that may or may not come this september...