Keep it, it can give you an edge in all sorts of price negotiations. Also dress down when meeting the other party. They will stop thinking they can pull money out of you. A friend of mine does it to the point where he even gets cheap rental cars to meet sellers (he’s in buildings). He would never show up with a new iphone there. What you can also do is have a good strategy, study the situation upfront, listen actively and be patient. Your broken phone is a good start, but don’t expect it to bargain for you. Anyway, hope this helps - best of luck!