Two audiophiles walk into a bar. They both sit down and order a beer.
The first audiophile notices that the second has affixed some sort of patch to the outside of his glass. He raises a questioning eyebrow. "What's that thing on your glass?"
The second audiophile's eyes light up. "I've been enjoying beer for 50 years now, and I've never experienced anything like what I taste with this magical patch on the side of my glass. One sip with this on the side, and the veils between you and what the brewer intended will be lifted. It's almost a spiritual experience compared to drinking beer without. It's made of rare white squirrel fur, sprinkled over with diamond shavings. It was an absolute steal at only $10,000 given the impact on the taste. There's only a few people in the world who even know how to make them."
The first frowns. "That is scientifically impossible. There is no way that patch has any effect on the taste of your beer. You spent $10k on what amounts to half a koozie, and not even a good koozie at that."
The second audiophile nudges his glass towards the first. "Take a sip. Prove it to yourself. Your jaw will hit the floor after the comparison to what you are drinking."
The first holds up his hand and shakes his head. "It wouldn't prove anything. Even if I could taste a difference, I wouldn't be able to trust that the difference was real."
"What do you mean?"
"I've seen the patch on your glass already, which has biased my taste buds. Even if your beer tasted significantly better than mine, which I guarantee that it wouldn't, that sighted bias disqualifies my experience. Without a proper blind ABX test, any taste comparisons are meaningless."
"So you won't even take a sip?"
"I don't need to. It's all bullshit."
Both audiophiles glare at each other, having decided that the other is a complete idiot. They spend the rest of the evening arguing.
Neither one of them touches their beer.