A local dealer has electronics built for him according to his rough specifications on design and his choice of parts. From years of experience, he knows what parts he likes in the electronics, but, the process still involves parts swapping to get his idea of the right sound. This may or may not involve expensive boutique parts. I saw a speaker under construction where one week, the crossover contained a very expensive vintage paper in oil cap, but the next week it had been replaced with a modern film cap; I joked that he was cheapening the design, but, he replied that the prospective buyer wanted a different sound that the modern cap would supply and that it wasn't really that cheap a part (it was a $400 per piece capacitor).
This same dealer sold his own proprietary amplifiers. I was asked to give comments on a particular amp, and I had to frankly state that it was far from his best effort. He laughed because it was an amp that his customer had sent to an "upgrader" who filled it with expensive Blackgate caps thereby ruining the sound. The customer was also disappointed with the upgrade and brought it in for the dealer to undo the damage. This dealer often gets in brand representatives who want him to listen to something that he might carry in his store. He has correctly identified parts in the electronics from their sonic signature; he can tell when Mundorf caps are in an amp or speaker; he thoroughly hates their sound.
The right part may be a boutique, expensive thing, or it may be something cheap and common; good designer/builders listen and pick what sounds best.