I have bought a few sets of wheel centre caps from eBay at about £10 for four, rather than £30 each for BMW 'originals'.
I am 100% convinced they are identical. I have compared the old 'originals' that come off to the 'fakes' in every way and they are identical (at least the ones I bought have been). Even down to stamping of info on the underside. I am convinced they are the same caps, just cheaper.
AND they last just as long as the expensive ones, if not longer.
And then we have the BMW 'original' wheel bolts at around £5 EACH. Bought two sets of 'fake' bolts, £17 for 20. They are identical aswell.
BMW don't make plastic badges, or wheel bolts. They out-source pretty much everything. So who is to say that the factories where they are made aren't keeping a few back and selling them on. Or, if they are copies, the technology to make a plastic badge and mould some steel bolts with a thread cut into them is hardly rocket science, so I am happy with my 'fakes'. Long may they continue.
I used to work in this area, and it could be a nightmare to explain to the newbies what was, and what wasn't, a kosher part. Fit, Form and Function. Fit is obvious, Function is obvious, but Form is much more than just dimensions, it is also the quality of the materials and the craftsmanship.
That last paragraph is an example of IP theft if BMW had outsourced the manufacture of the badges and had not given the company the manufacturing rights. Only BMW and the company know what the arrangement is.
Some companies (the likes of Hella) usually have the contract to manufacture in their own name after a certain amount of time. This is how you can get the same part, made by the same company, but without the BMW logo. OEMs tried to prevent us using these parts (and void any warranties), as Form was different, since it didn't have their logo. They won their case, and we stopped using them whilst in warranty.
Copyright for parts usually expires after 10 years, and anybody can make anything. The buyer has to use due diligence to determine if a part is of sufficient quality. I've just bought a pair of 229mm drop links (box says Borg & Beck) for my M. The advert says they are for a Land Rover. On inspection, they look to be of sufficient quality, but I'll never know for sure.