https://finance.yahoo.com/news/iphone-users-already-starting-ditch-month-old-iphone-8-122610995.html
The site says 7% of thousands of the iPhones it bought in the past month were iPhone 8s, while in the same period last year the percentage of then-released iPhone 7 was only 1%. A 256GB iPhone 8 can be traded at up to $500, less than one-third of the retail price of $849. After October 27, the pre-order date of the iPhone X, the trade-in price is expected to drop by 30%.