What is your experience with the law of diminishing returns ?

Who you writin' at? me?    Writin: "  So you are saying every time you spent more on something and did a comparison , the more expensive item sounded better ? "                            
Who wrote that you did, not me.  If your bias wants to read that into the lines... not my problem. But I CAN mention an example of the opposite which happened to me. Around 2010 I bought the all new Brsyton DAC. Raved in TAS AND Stereophile. How can I go wrong?? Got it home and sound is no better than the old bought used for $250 Adcom DA700. Something MUST be wrong with my system!!! So after weeks of trying to discover.. well the Bryston was just no damn better. So I returned it.Now if I was a true believer, I would have automatically known the Bryston IS beter, because TAS and Stereophile said so. and it cost TEN TIMES what my old DAC cost. Didn't happen.

Elizabeth . It is in response to the ops question . I can only think he has tried a few pieces to have that experience .

All it took for me to figure out more money does not mean better sound was having the realization that a professional studio does not have such a component called a preamp . I visited a studio when my step father was recording a cd . I was in the control room listening and asked the engineer what preamp they used and he laughed at me , I was picking his brain about hifi for my system . He told me I needed to get a volume pot and I'm good. Took his advice and it has worked out quite nice .
There have been times I have tried preamps since that day 15 years ago . Tried a $7000 marantaz, trusty old volume pot sounded better . Handful of other preamps along the way as well . So glad I came to the realization on whats important to me . It allowed me to buy speakers that were out of my budget 

I think that the issue is in large part, how much and how do you want to teach your ear/brain mechanism to listen for?

Are you teaching your brain to be happy, or are you teaching it to discriminate among cables? At a certain point, sure, you are becoming more and more sensitive, but to what end?

The law cannot be applied if you got the wrong component, including cable, regardless of price.
The system doesn't have to be high end for you to hear even small differences, but it has to be good enough and very sensitive.
No experience or "brain teaching" is needed.