The exact location of the zone of diminushing returns is function of your past subjective experiences and function of the actual progress in engineering...
But this zone exist , its size is relative to many factors tough....
The basic fact of our audio life is that there exist level of technical engineering S.Q. and limitation of the amount of money available for upgrading ALL the components of an audio system to a new level of S.Q.
The question for most of us is then how can we approach a "good enough" S.Q. with low amount of money ?
The answer in my experience is it is possible to reach a "good enough" S.Q., with a strategy of embedding implementation for any audio system at any price.... This embedding strategy in my experience often exceed in positive results the costly upgrading strategy that most of us consider the only way....
If you had a relatively already good system the chance are that you dont know what this system is capable to give at his optimal working capacity rightly embedded, mechanically, electrically, and acoustically....
The most important factor for the embeddings is for sure an audio dedicated room, it is more important than the purchase of any electronic component most of the times....
The influence of the marketting propositions linked in some case to some quality increased new tech mask the most important factor in audio life : the ways to corrrectly embed your actual audio components which is the less costly and better way to improve your system and put it on another level without asking for new costly technology....
This is my only discovery in my audio life.... My listenings experiments and simple homemade devices gives me a totally new and high level experience with the same unsatisfying system i bought few years ago which is now so satisfying that upgrading it, tough possible for sure, is without real appeal.... Because with a "good enough" system you listen to music not sound and your are no more bothered by your system apparent limitations....These actual limitations of my system are no more the same limitations because they were cured by the cheap embeddings devices controls now...
My system is not the best of the world but when you listen to a symnphonic mass, distinguishing, the strings mass, the wood mass, the brass mass and the voices mass, with a natural timbre, you dont think anymore that with 10,000 dollars on a new electronic component you will be more happy.... You listen music without be frustrated thats all....
For sure buying a good speakers and a good amplifier and a good dac is a challenge but in no way too difficult if you inform yourself.... I know for sure because it was the easy part ....The other part is more difficult and ask for listenings experiments and faith in yourself and not more money....
I hope my message will make some newcomers to think and refrain themselves to throw money.... It is more fun to do it yourself and i can assure you that is is possible.... I am not technically more educated than most of you, i am not more skillful with my hands than most at all.... You must listen, think,read and try with low cost available materials and devices....
God bless you all.....