your statement made it sound like for $800 all you get is a screen. but obviously a phone is a lot more than a screen. people want high build quality products with 6-8 years of software support that apple provides. all android phones are broken in less than 2. android fans will defend even the crappies build quality plastic phones.
well lately google-samsung catching up with update support (7years)
but lets be honest, that apple long software support isnt that great, look at how much feature for older phones they cut each major release
for build quality, well if you bought phone with similar price range (albeit cheaper) say above $500, it will last as long as iphone
and metal-frame is not equal to "good" build quality, i mean bend-gate with metal frame happen , so
+ if we consider cost to repair to iphone, while for cheap android phone, people can simply buy new one
its just matter people preference, but there no need to support apple-tax