Part of it is because of the no questions asked warranty. Take a Leupold that has scratched up lenses, dented main tube, and frozen adjustments. Send it in, and you will either get a working scope back or a replacement that is usually a higher value than the scope you sent in, at no charge.
Try that with even an expensive brand like Swarovski. Good luck. They will bill you for whatever needs repair that isn't "warrantied", which would probably be everything. And, lately they have been refusing repair unless the serial number matches up to the current owner.
