That's about as logical as "Either the Moon is made of cheese or it isn't made of cheese. We know that it isn't made of cheese, therefore it is made if cheese" QED.
Huh?
You asked: (Vs the Benchmark amps)
why should anyone consider a 10-20K amp, particularly if it didn't measure quite so well?
My answer essentially covered that question.
You can have an amp that doesn't measure "quite so well" as the Benchmark, but that difference may not be audible. In fact, few amplifiers measure
exactly the same, but many if not most solid state amplifiers, run within their parameters, will likely have distortion levels so low you couldn't distinguish them (without knowing which was which).
But in the case one amplifier's distortion is audible vs a Benchmark, then it's
still possible one's preference is due to a bias effect, not necessarily the sound. The looks, or the technical claims made for the amp, or the brand name, etc, can influence what you prefer. That's a real thing; that's how humans work. But if it's the case someone truly prefers the sound of the added distortion, hey, fine, that's their preference and they may be fine paying "10-20k" for it.
I myself paid more for my CJ tube preamp than I could have paid for a perfectly neutral solid state preamp (It was more expensive than my Benchmark LA4 pream). Because I had a bias towards liking tube amplification aesthetically and I also might prefer a bit of coloration.
So your implication that I was just question-begging in some way doesn't relate at all to what I wrote.