I mean for software we talk about reproducability and versions down to the bit. But if a consumer products replaces one piece of metal with plastic it's apparently the same product?

Products should have versions that look like this.

2.1

* Replaces piece X with plastic. * Reduced frame width to save material costs.

This could also be positive and make it more transparent.

2.2

* Strength part X that breaks very often. * Change edges to reduce chance of injury.

I mean this opens a huge box of problems, I know apple didn't want to admit their keyboard was problematic in fear of lawsuits. This is how it should be.

My guess is that there are serial number / model number / revision numbers that do change when this is done. It is just not mandatory that these changes be published. I agree that it would be nice to know when metal gears had been replaced with plastic.

The frustrating thing is that sometimes it is extremely difficult to find hardware that doesn’t suffer from this quality fade. Buying decent router hardware comes to mind; if I want a non-professional router that doesn’t use the cheapest hardware possible, it’s very difficult to assess this apart from spending hours hunting down reviews etc.