I have to question this.
First off we need to determine what constitutes ‘non OEM’.
It is true that the vast majority of goods you have are made not only with components from more than one source but also in the same factory and same production line as the OEM ones.
What’s the difference between Brembo pads and BMW branded pads for example?
You have no real understanding of how manufacturing works, which is why you're questioning this.
First of all, parts, even if manufactured on the same line, have varying quality. Manufacturers specify various longevity and performance characteristics of a part. The parts generally go through testing to determine if they match those characteristics.
Parts that match those specs are considered A parts. As a synthetic example, Apple screens need to keep their colors true for, say, 2 years. A part may do that for, say, 6 months. It's not up to spec, but it still works mostly. And how long does someone actually look at the screen?
They'll sell that as a B part. Some screens come out with a color cast - it may be a bit blue, or a bit yellow after a month. That'll probably be a B part. Some have bad colors right off the bat. That might be a D part.
In Asia, you can choose the part/cost tradeoff. Most shops that I've been to will ask you how good you want your parts to be, and charge accordingly.
In the US, you get whatever parts your shop sells you. Most consumers are completely clueless and expect repairs to be used with "real" parts. Maybe they'll go back if the screen goes bad and get it replaced; maybe they don't.
The problem is when you pay "A" prices but get a "B/C" part.
And plenty of people will break their screen, then get a cheap replacement and trade it in/sell it.
I mean, don't you wonder why there are different prices for the same thing? It's not all marketing.