It's the same problem with the bike industry.
But there is one thing which differs.
Big brand manufacturer A says:
New for 2020, our XYZ mask specially developed by our RnD to have this kind of property to achieve this and that. It ends up being an off the shelf aropec mask with a new logo.
If they actually like make a specific new tech, and then hired problue/aropec to make the mask since they're super experienced with it. It's fine to charge a premium price for it.
And then on the other hand a manufacturer like Cressi or Mares, has an X-view or Calibro like mask, which they actually have some new improvements, and some changes, and they charge the same price for a objectively higher quality product.
I recently got a calibro. And the mask is super high quality, and just having tried it, actually works super nice. And for that same price you can get a scubapro/aqualung mask which is a rebranded OEM mask. And compared to several different masks in that price bracket, I don't see why someone woul pick the other one.