I come from looking in to fringe beliefs since the late 80's or so, and one common thread is you can debunk someone's belief until the cows come home, and they'll still believe.
Absolutely true.
I think for a true believer, resisting attempts of "coercion" and standing their ground is part of the whole point of believing. Humans are really weird in this regard, especially once they found a few peers that share their belief and create an echo chamber.
Do I think every salesman in an audio store, that talks to me about how e.g.: "an amp needs a beefy toroid in order to sound good" is an evil, mustache twirling villain that has it in for poor wallet-kun? Of course not. Though many will try to "upsell" you, even if they know that the difference in products is marginal at best. Honest ones that tell you e.g.: "the more expensive item doesn't really do much in your particular use-case." are rare.
The seller in your mom & pop's garage audio shop, most likely, doesn't have the education necessary to cut through the marketing BS.
However:
I think most of the ones that produce these things do. They KNOW. They designed the useless, overpriced gadget. They came up with the marketing blah. And yes: I am sure they also measure. Not publicly but in house they definitely do.
So yes: I do hold them accountable in a sense that companies who do shady stuff do not get my cash.
Not much else I can do, except point anyone I meet to this forum. An isle of reason in a stormy sea of emotion driven marketing.
Yet audiophiles who are not selling all this tweaky stuff, only buying, will report their impressions of cables etc in similar language. That should indicate that spouting nonsense like that doesn't entail subterfuge.
Most audiophiles have 0 technical knowledge, as it is not a requirement for the hobby. So you really can't fault them too much. They get fed nonsensical data that creates bias and then human nature kick in re-affirming said bias, after all what all the other members hear must be true the Kilobuck cable must do something, after all.
Not everyone is wired like me, that has no qualms to go on head-fi and tell them that I cannot hear any difference between Focal's fancy Clear cable and a 5 bucks Amazon extension and then shrug off the laughter that ensues. :'D
I expect a little more from vendors and
equipment producers especially.