I stooped reading right here.
In the world where I live plastic is everywhere.
And by premium I don't just mean build materials. It's an entire combination of Design, attention to details, elegance, materials etc. And for me Apple does tick the boxes on all these. Obviously you and many guys here are free to disagree.
It's funny because in the world I live in Metal is everywhere.
Cars, Food and drink cans, trash cans, cutlery.
I would hazard a guess that Metal is way more common a material, if you wish to clump all metals together (as you seem to wish to do with plastics) as a material.
Aluminium is the most common element in the earths crust.
It's all a made up concept this idea of quality and material.
Anything cane be made good or bad out of any material.
Plastic can be made super strong and resistant to damage.
It can have a lovely feel in the hand, grippy, warm, smooth, shiny, matt, whatever you want.
If I wanted to use your logic, I could say iPhones are made from the same material as fizzy drink cans.
Does that make them premium?