How much should I sell my used iPhone 5s for?

So I have an iPhone 5s, and I want to upgrade to the 6 so I want to sell my current phone. It's a 9 month old phone. Barely has scratches on the back, however it has tiny dents and scraps on the corner/sides of the phone. The front and back camera aren't as good as it was when I first bought it, because over time it collected dust. Idk how, but it did. I mean the quality isn't **** but it's a tad fuzzy. That's absolutely no scratches on the screen, however. It still has a screen protector. Everything else, such as the mic, headphone jack, speakers, ear thing, all the buttons, they all work. How much would YOU offer for this phone if you wanted it? I don't want to let it go for cheap, or too high!
Added (1). the finger scanner also works perfectly, and the phone is upgraded and everything.

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