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.
Audiophile are buying it for better audio, but the quality isn't actually better.
Keyboard enthusiast buy it for different materials, finishes, color scheme, sets of switches, sets of keycaps, etc... They all can be done in a better or inferior quality.
I wouldn't agree with it because it's mostly defining the object by its aesthetics features.
As a disclosure, I own expensive audiophile gear, but, again, for the aesthetics primarily. I would be much happier with audiophiles if they just said they like the aesthetics.
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+.
1. Switches (can be lubed or spring swapped to customise feel) 2. Plate (holds switches together, can be aluminium, carbon fiber, brass, polycarbonate and more) 3. Case (heavily affects acoustics) 4. Foam (put in case to affect acoustics)