Placebo really is that potent & prevalent. People are going about this wrong by arguing that people like this aren't having the experience they claim. If you could somehow measure their brain activity in a known, non-blind A/B test, it would indeed be different when they claim so.

However, the actual cause of that difference isn't the equipment, it's the belief. They press play on that player, fully expecting to hear a difference, and their brain adjusts their perception to meet that expectation.

If you look at it from that perspective, it all makes much more sense. Every amp, every dac, every cable, every bit of snake oil- they really do perceive a difference, but the actual cause of that is their own mind morphing their experience - placebo - not an actual effect of the equipment in question.