At one time you could do pretty well selling the old phone on Ebay or Craigslist but in the past couple of years the demand hasn't been as strong on a used iphone. Sites that resale the phones are buying up a lot of the old phones and driving the used prices down. So now paying over $900 for the 128gb 6s and selling the old 128gb 6 in many cases will only bring a little over $300 for the used phone so it still makes you put out about $600. I use to make money selling the old phone and buying the new phone and that's why I did it. Now it cost me money so I don't upgrade as much.