It’s not what you’d expect from Apple, but there it is: your older iPhone is worth a bit more than it was before if you use the company’s Reuse and Recycle Program in June. There is a “problem,” though: the value “jump” is limited to the US (via 9to5Mac).
Anyway, if you happen to live in the US and want the latest iPhone, you can receive a gift card to purchase one. Its value depends on the iPhone model you bring in for the Reuse and Recycle Program.
Depending on the condition of the iPhone, Apple will pay a maximum of $50 for an iPhone 4S — up from $35 — $100 for an iPhone 5 (up $15 from the previous $85), and $200 (compared to the $175 paid previously) for an iPhone 5s.
As you can see, Apple is not willing to pay the price you may be able to get by selling it on eBay. A 16 GB iPhone 4S sells for $100, but you can get as much as $195 for a 64 GB version. If you own an iPhone 5, you may get more than $200 for the entry-level 16 GB model, while the iPhone 5s models start at $300, but you can sell them for as high as $400 if you have the time and patience.
So, ultimately, it’s up to you.