That calculation is contingent on the endpoint in both cases being "selling the old phone". I tend to hold onto all of my old phones and computers (still have

That calculation is contingent on the endpoint in both cases being "selling the old phone". I tend to hold onto all of my old phones and computers (still have 10+ year old MacBook Pros and iPhones going back to 3GS), so the residual value is $0 in both cases.