I'm interested in iPhone you have for sell. 
Wonderful! It is in great condition and I would be happy to meet up with you directly at the spring store to ensure the clean ESN so it can be activated same day. Would you be able to pay in cash and meet me at the local store.
The Iphone 4 isn't supported by Apple anymore.  I was wondering if you would come down on the price.  Maybe $50 since it can't run the current operating system?
Well, It could always be used as a trade in since Spring has many deals that will provide you discounted pricing for having a trade in device. Would you be willing to meet in the middle and call it $75?
The trade-in really isn't worth much either way.  Do you have some cases for it?  If you can throw in some cases and include Apple approved charging equipment then I can do $75