How much is a used iPhone 5 worth?

My friend is offering to sell me a used iPhone 5 (black 16gb). He has jail broken and unjail broken it before. It has 1 crack on the back top glass area, not too bad and doesn't affect the camera. It will come with the box, cable, and charger. He s charging 50$ at the moment and I'm the only buyer. He isn't anxious to keep it or sell it.

Added (1). i need a real answer other that the first three

It depend how long have you been used

A crack means dropped, so who knows what damage was done.

The rate is not bad,
Just convince your friend to reduce some, maybe min-max 2-5$.
Its not a bad deal…