Sprint has lowered the bar in The Great iPhone 6s Price Race of 2015. Trade in an iPhone 6 at a Sprint-branded store and snag a 16GB iPhone 6s for $1 a month. Or, trade up to a 16GB iPhone 6s Plus for $5 a month. If you need a little more storage in your mobile life, get a 64GB 6s for $5.77 a month or 128GB for $10.53 a month with the trade-in of an iPhone 6. For 6s Plus people, 64GB runs $9.77 a month and 128GB costs $14.53 per month with a trade-in. There's also a discount for swapping out your iPhone 5s: Get a 16GB iPhone 6s for $10 a month or a 16GB 6s Plus for $14. All of this is part of Sprint's (totally-not-creepy-sounding) iPhone Forever program, which allows eligible customers to grab the newest iPhone model as soon as it's on the market. This requires a 22-month lease on a new or upgradable line, alongside the trade-in. Before Sprint's announcement, the cheapest monthly iPhone plan was T-Mobile's $5-a-month trade-in offer for the 16GB 6s.