What is your experience with the law of diminishing returns ?

For those of us on a budget - is the new thing REALLY five times better than what I have now?

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?