There’s all sorts of complicated economics surrounding when and how and where you should upgrade iPhones, but T-Mobile’s trying to make the math a lot easier: trade in an iPhone 6, and you’ll get a 6S for $5 a month.

The low-price deal relies on you trading in an iPhone, and taking out and JumpOnDemand plan. Normally, those plans start at $20 a month for a 6S, so it’s a decent discount. If you trade in a 5S, it’s $10 a month, while any lower-spec device will be $15.

T-Mobile is pushing hard to be the carrier of choice for the iPhone 6S, offering cheap monthly instalment plans and steep discounts on the phones. Sure, there’s still questions about the company’s network coverage, but if you’re not so concerned about always getting reception, the plans are starting to be a no-brainer.