Value - Beholder
If somebody pays $350 for a wooden volume knob and says it improves their $5k preamp sufficiently to justify the price, who are we to say it doen't have value? The concept of value is in the ear of the beholder. Many people worldwide would be in disbelief with ANY of our systems and how much they cost. They'd perceive the value of some metal gadgetry vs. their need for food as zero, unless they could sell it.
Granted, that's not our reality, and our society allows for such niceties without sacrificing food or shelter. But, the question of Value is one that is entirely personal and situational. Does this sentence make sense: "That item has no value to you"? No.
You won't convice the knob-owner he's wrong, nor will he ever make you believe there's a difference. The discussion (if there is one with this person) is doomed from the start, much like religious or political discussions that never convince the other side. This comes down to the gaping yaw mentioned earlier.
Where a particular "believer" or nonbeliever draws the line is their personal choice. I doubt there are many of us that believes every single [fill in blank] is beneficial and suspect very few of us (not here, but generally) doubt every single [fill in blank] is immaterial.
Again - discussions of probable merit are valid, slamming customers as dumb or gullible is pointless. It's their hobby too, and they get to decide how to enjoy it, as Jaxvon said. They aren't spending your money and you don't have to live with their system, so give these folks a break.