I plan on upgrading to the iphone 6s come September from my iphone 4S. Where is the best place to unload my old iphone? Was looking on eBay and some people were selling for $100. My phone is in great shape (some slight scuff marks on the back) so imagine I could get at least $75 out of it. I don't plan on selling until I have the new one in my hand so that might bring the price down quite a bit, but I need a phone so really can't sell until I have the new one. thanks for the help guys PS - any advice on what I can use to clean off scuff marks on the back of my iphone? I've tried a cloth (which helped a little) by scrubbing it, but would really like to sell in great condition. Seems like they are light scratches that just don't want to come off.