@ghdprentice , It is not so much a matter of diminishing returns as it is value.
There is equipment that is a much better value than other equipment of similar performance. Much of this "value" equipment is still plenty expensive. There is a category of "Luxury" HiFi made purely for very rich people who have to drive a Rolls or have it driven for them. Much of this equipment is needlessly complex and over built with things like 300 lb CNCed chassis. I put that stuff in the same category as a Rolex watch. An Apple watch is more accurate and you can put a Mickey Mouse dial on it. You can see Rolex watch wearers a mile away. Their left arm is two inches longer.
Media people have to extoll the virtues of ultra expensive equipment. It is their job to do so and their revenue depends on it.
If it costs more it sounds better because it costs more. Many media people have this programing. They did not experience the lowly Roger's LS3 5A
Lastly, we frequently view the past with rose colored glasses. I fondly remember several systems. They were excellent in their day but I shudder to think what they would sound like today.