I've tried several online calculators, browsed through 12 pages of topics on this forum and read a half dozen reviews and it seems that many folks would have a similar question I can't find the answer to.... I want to swap (sell/trade) one 32GB iPhone 5s for a 64GB 6 and I want to add a new line with a new 64GB iPhone 6. I have an 8 GB / month plan currently. I am happy to pay cash up front for the full retail value, buy a subsidized phone or the much maligned Edge - whichever makes more financial sense. I'm happy with Verizon and expect to stay with them for two years or more. I expect to keep these phones for up to 2 years. Currently I have three iPhone 5S phones that are 9 months old (15 months remaining on contract) - none available for a subsidized upgrade anytime soon.