When your post starts with "educated about what?" just assume we're talking about you at that point.
Yeah, what he said.
It has been discusses in this thread and others. Various physical properties of many different "plastics" and metals, along with varous manufacturing methods, steps required, costs, design considerations, etc.
You cannot say a "plastic" back is cheap, as a blanket statement, without looking ignorant. Unless you have procurement pricing data, or have a pretty good understanding of the actual source material, design features, casting methods, machine setups and operations, finishing techniques, etc. of a particular part.
Whether or not a particular aluminum part is better, and/or more expensive, than a particular "plastic" part is likewise subject those and other criteria or factors relating to their design and what duty they will be subjected to.
Now I'm perfectly okay with you saying it "feels" cheap. That's obviously a personal opinion and I can make no argument against it. But it is at least in part driven by your preconceived notions.
I happen to like the HTC One because of the aluminum design. I love the look, and have read that it feels very rigid/solid. But those qualities are in the asthetic/ergonomic category. I've no doubt that it is a thin and flimsy part, made to feel better both through the fact that it is curved and the fact that it is glued to the more rigid and tightly packed innards of the phone. Just because I like it subjectively is not a legitimate reason to claim Samsung's parts are cheap or inferior.
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