ios vs android

Why second hand iPhones cost more than second hand Android phones. iPhone 7 came out three years ago. I could sell it and still get a couple thousand rupees. But when it comes to Android phone, it would be a very different. Why can I get so much if the phone is 3 years old? Right now on OLX a used iPhone 7 goes for around 20,000 INR to sometimes over 30,000 INR . But a Galaxy S7, which also came o...