Re: Affordability my arse
You have a faster CPU and a slightly better camera, which you get any time you get a new phone. Nothing particularly amazing there. I've never heard anyone complain that their existing iPhone 5 is too slow. The iPhone 5 camera is pretty decent, but it isn't the best, so Apple are playing catch-up here.
So you have a fingerprint sensor to replace the lock screen pin and iCloud password. Maybe it is better than some of the fingerprint sensors I've seen in the past that didn't really work. We will see, but it isn't really a compelling reason to buy a new phone.