It can be argued that the midfi audio market wouldn't exist if everybody
believed that all amps sounded different and only the really high priced
amps sounded good.


I think it would be a weak argument. there is no debate that speakers sound the
same yet, many midfi inexpensive speakers are chosen over more expensive
speakers that sound better to most listeners. Many people who believe that amps
sound idfferent opt for less expensive amps. Economics are a factor even in a
world where everyone believes everything sounds different and the more
expensive stuff is believed to be intrinsically superior.