Earlier quoted context omitted.
The key difference being audiophiles often fail A/B tests comparing audio quality. You would definitely notice how nice an expensive mechanical keyboard feels. Whether you think that is worth luxury pricing is another story, but the quality is at least more immediately appreciable.
I would be interested in seeing an AB test of keyboard enthusiast between say a 200$ keyboard and one that is 5x as expensive. Audiophiles also claimed that they would definitely notice a difference.
If you wanted to test, it should be on equal footing. A $200 keyboard with the same switches and modifications as a $2000 keyboard. Same keycaps as well.
If we're talking kits, honestly you might even want to use the same board and just have the case be different.
Even with all that, there's a good chance they will be able to tell that the keyboards are different, simply because the acoustics of the cases are going to be different. They just won't be able to subjectively measure the quality.
$200 might be too low though, I think the realm of it not being noticeable is probably closer to $300-400+.