How much will an iphone 5 cost without an upgrade?

I dropped my iphone in the pool (I had a lifeproof case on, but apparently it wasn't on well enough) and now my phone keeps unlocking and locking on its own and screenshots nearly everything. My lock button won't work when I try to use it either, but the phone will lock by itself and it's getting rather annoying. I'm not eligible for an upgrade until January 2015, so how much would it be to buy a new iphone 5? My whole family already has contracts there, we just aren't available for upgrades.

A few hundred dollars depending on hard drive size. Maybe $600 or more?