What is the general resale value on iPhones?

I don't think applying anything with an adhesive necessarily means the coating will be intact. If someone tries to remove the protector the coating will come off to some degree.

It might be worth something, but it's depreciating as soon as you bought it. If it's in good condition and never gets any aftermarket parts then I'd think it's still worth a few hundred dollars. However, an iPhone will rapidly lose more value for every new iPhone that comes out. That's just the way technology is.

You're right, you might as well apply the new car theory to this. As soon as you drive it off the dealer's lot, it's depreciating. As soon as you take it out of the box, it's depreciating.

I will say this, and we've covered this before (you and me y_p_w). If it's locked to a provider, you'll get less for it. If it's unlocked, you'll get 30-50% more for it, because of the fact it's unlocked.

The way technology is? You hit the nail on the head.

You can check the buy back value for devices yourself - the Apple recycle program gives estimates, as will gazelle.com, Amazon.com and other for-profit recycle and buy back sites. Not all of these buy-back sites are buying in order to resell or recycle for their own profit. So of course they are not going to offer as much as you are likely to get selling it yourself.

As as with most things, it will depend on market demand, features and conditions of devices. It’s not something that anyone can predict with any sort of reliability or accuracy years out.

Check here (in the U.S.) for a general idea. Of course, you can do somewhat better if you sell it yourself.

Renew and Recycling - Apple

Cars hold their resale value much better than electronic devices though. But buying any kind of electronics and worrying about how much it’s going to be worth in a couple of years is self defeating.