i concur with your post description...
I will only add that sound perfection does not exist and as you said it is true ...
But the acoustic factors scientifically really exist that described all aspects of good sound in acoustics ...
Because most people focus on gear price tag for audiophile experience not on acoustics factors which are way more deep than only room acoustic , they accept to spend money but they dont invest the big amount of time in the acoustics necessary studies and experiments ...
They became then obsessed fetichist and brag about their fetisch chosen object sold by them as a solution to all problem ( for exemple EQ or cables or tube amplifier etc ) ... The gear and cables are their hobby ... My hobby was for few years acoustics thinking and experiments to create a good audiophile experience at any price with anything reasonnably good and with synergy for sure to begin with ... Acoustics principles and facts dont change with price or specs of the gear ...
And for those who dont know how to read, i dont claim that my speakers at low price beat more costly one in performance ... I claim that there exist a minimum acoustical satisfaction threshold and we can pass over it at low price if we understand basic acoustics ...
There is definitely a Rule of Diminishing return just as there is the Sunk Cost Fallacy. I suspect that the Venn diagram of those two circles would be close to one circle in some cases for certain audiophiles. For example, someone subconsciously suffering from the Sunk Cost Fallacy has spent years and enormous amounts of money in their pursuit of perfection and yet never attain it as perfection does not exist. So each subsequent purchase is rationalized as moving closer to audio perfection. Yet the reality is they would not / could not admit - even with hard facts - that the recently purchased $100K speakers are marginally better or equal to the $10K speakers or even the $5K speakers because they suffer from the Sunk Cost Fallacy. The diminishing returns set in long ago for each dollar spent.
The Rule of Diminishing Return applies to many industries where the marginal performance gains do not justify the cost, yet at the high-end market of consumable goods, the real reason is justification for many that they can exhibit how they can "afford" to pay $150K for certain speakers, or $200K for a vintage Jaguar, or any luxury item for that matter. Some may actually know they’re getting no real qualitative improvement for their investment because the point is to exhibit their wealth.