What is your experience with the law of diminishing returns ?

Without any reference point, this is a tower of "Babel"; it's like asking the question; "How far is it from here to Chicago". Where is here? If we don't know that, what's the point of the question.

I suggested a reference point that I know is valid, and even if you disagree, I would hope that you at least know what it is; so far this is a totally meaningless conversation.

Inna, if I was rolling in dough, I wouldn't buy a 10K power cord, and since I'm scientifically inclined, I would not even buy a 1K power cord; where's the science?

In order for a question of this nature to have any meaning, reference points will have to be established; at least one well known reference point is the "Stereophile rating". I have subscribed to "Stereophile" for years, and I consider their rating system to be valid; for example a component that's rated "Class A" will sound pretty good, that I guarantee.

I try to buy the cheapest component that's rated Class A; I believe components that cost more are entering the land of diminishing returns.

In order to confirm this, I would need to buy more expensive components; until that happens, I can only guess whether or not this is valid.

30 years ago, I walked into a high end emporium and heard audio "holography", just recently I acquired it. This is the point of diminishing returns; it's impossible to put a dollar figure on getting where I am, that's because money and knowledge are interchangeable; I put a lot of time and study into this endeavor. Many will never get here, many more, like the fox and the grapes, will say "That's not where I want to be".

Once an audiophile gets here, the question is, how do I make it "Mo better"? And the answer is, "I need a pound of money".