Funnily enough, it is widely acknowledged in the electric bass community that, once past a certain price point, spending more to buy a "nicer" bass gets you only marginal return in the quality of music you can make with it. The solution to getting a nicer sound is usually not in buying a nicer bass. Yet many still save for boutique and custom made basses that cost north of 5000 dollars.

The difference is though, if you like a bass very much and it is comfortable for you to play, you would spend more time playing and practicing it, which I think is exactly the point of buying a mechanical keyboard (at least for me). It makes working on it more enjoyable.

I notice you are generalizing the guitar analogy but then being specific about mechanical keyboard.

I am more efficient and effective with my (generalized) keyboard at creating input for the computer than a cheap because of factors like: I can customize the layout in ways that match my specific work and habits, I can individually adjust each hand of the keyboard, I can reduce the likelihood of RSI...

Yes, there may be non-mechanical options that address some of these issues, feel free to show me a non-mechanical that is easily programmable, supports "z if tapped, control if held", thumb clusters, and split hand ergonomic tilting/tenting. I haven't seen one.

So forget enjoyment of the user, I'm confident I'm more effective than I'd be with a $10 membrane keyboard, especially when measured over the lifetime of my career.

There is a lot to a guitar. Players can be particular about the type of wood used on their fretboard, if the frets are slanted or not, if there are frets, floating bridge vs fixed bridge, locked tuners, intonation, weight, feel, electronics etc.

The guitar doesn’t make the guitarist but when it is a labor of love some do really care about these things.

I see you have not had RSI yet.

That's not the whole purpose though. Besides having a better sound, expensive guitars also "feel nicer" to play. A professional guitar player could easily detect a cheap guitar by just playing it without hearing it.