How much would an iPhone 5 be without upgrade?

My iPhone 4s was stolen a couple of weeks ago, and I really need another one. It turns out that it would cost me between 400 - 450, says the at&t clerk. I upgraded to the 4s back in March, and I'm under a family plan with my mother. So I was wondering how much the iPhone 5 would cost me, if the 4s is $400. Logically, it would appear that it should be $100 more, right? Since the iPhone 4s is $99 and the iPhone 5 is $199. But, nothing makes sense to me anymore. I hate my life. Losing an iPhone is like losing your house.

Added (1). So you mean to tell me that I will be paying 400 dollars more for an iPhone 5 than an iPhone 4s. I think I'm gonna be sick.

Its $799 without an upgrade.