My point on weight was that the market for that it is common, which is probably a stronger statement than needed. I should have made the weaker argument and said the market exists which only needs one example. The company Beats can serve as that example, this company sells the majority of premium headphones but I don’t actually know what percentage have weights placed in them. I am assuming a non trivial percentage.

You are using circular reasoning in your logic, you assume the premise is true and from there you derive your evidence.

I would contend that someone thought about it and decided to go with the cheaper option because they could get away with it. I would consider my assumption to have more grounding given my experience with manufacturing and cost accounting.