Have you ever wondered why used iPhone's cost so much money? Used iPhones like the iPhone 7 or 8 almost always cost more than the same generation of Android phone. Since iPhones receive support and feature updates longer than Android phones they often have a higher resale value. Apple still supports older phones like the iPhone 6s, which will be updated to iOS 13. But older Android phones like the Samsung Galaxy S6 don't get the newest versions of Android. Android phones like Google's Pixel phones or OnePlus phones that receive updates faster usually perform better in the long run.
iOS compatibility chart via Statista: https://www.statista.com/chart/5824/ios-iphone-compatibility/