This is not a recycling program. A third-party company, Phobias, sends boxes with return labels and pays a little more than the other buy-back businesses. They will most likely refurbish them and resell them for about twice what they will pay you. Of course, if that sits wrong with you, then you can sell on eBay for the better money. So this is more of a trade-in program than a recycling program.
I've already sent in three items I no longer needed/used. I did check resale values on eBay as well as other buy-back companies like Gazelle.com. I traded a 2015 MacBook for the new MBA. I have sent in another 2015 MacBook and a 2011 MacBook Pro. Not much value left in the 2011 model. I'm thinking seriously about trading my 2015 5K iMac for a new iMac i9.