I've used a website called Swappa which has my exact iPhone 5. White Verizon 64GB (not including my cases and unused applecare until 2015) for near and above $600. I have two Lifeproof Fre cases, Otterbox Armor and other cases. I'd imagine my value is around $700-800 or more. More than enough to buy an off contract 32GB-64GB 5S when it comes out.
That's my plan anyway.
Take care of your investment and it takes care of you!
That's my plan anyway.