What is your experience with the law of diminishing returns ?

Chapter 13 !

methinks I could spend about $6000, and for my ears I would have a real kick as Hi Fi system to satisfy my needs.
So, $6001+ is my price point of diminishing returns.

I had musical training for ten years, starting at age 8, so I believe that I have a pretty good ear.
Last year, I had to make a choice between the Magnepan 1.7i's and the 3.7i's.  The 3.7i's are more than twice the price of the 1.7i's.   I auditioned both models at Take5 Audio in New Haven.  While the 3.7i's had a bit more bass extension, I actually liked the high end of the 1.7i's more.  In my opinion, the difference in the sound didn't justify spending more than twice as much.  I've had the Magnepan's for a bit over a year, play vinyl and SACD's, and I'm very satisfied with them.  There is a point in high end equipment where the equipment is so excellent that spending a hell of a lot more doesn't improve the sound appreciably.  

This is unusual, I think, same brand speakers for half the price being preferable overall. Were the electronics source and cables the same when you were auditioning ? 

My experience with "the law of demising returns" is that its an abstraction at best, with no basis in reality. One simply cannot say that more money buys less incremental improvement, for the simple fact that we all know of components that cost less but sound better. In all those cases not only does spending more get you a bigger return, even spending less will too! Its just one of those loopy fantasies people won't let die. For what reason I haven't the foggiest. They should. But they don't. Oh well.