https://www.cnbc.com/2018/11/28/apple-increases-trade-in-value-of-older-iphone-models.html

You might want to consider upgrading your iPhone now if you've been on fence about buying a new iPhone XR or iPhone XS.

Ahead of the holidays — an important quarter for Apple sales — Apple increased the amount of credit it's willing to offer customers who are trading in older iPhones towards the purchase of the new models it launched this year.