The law of diminshing returns?

At what point, do you say, no more, Basta?

That’s really only answerable on an individual basis after listening to a given product preferably and optimally in your own system.  Fortunately DACs lend themselves well to buying used, which to me is the way to go for the more value oriented with relatively low risk.

I think the audiophile ultimately achieves a balance between price and enjoyment quality. 

In that equilibrium is satisfaction- at least for the individual is able to be satisfied.

When people talk about diminishing returns in hifi, what they really mean is that there’s a limit on how much they personally would be prepared to spend on it. That’s fair enough, but it isn’t diminishing returns. 

Diminishing returns can’t apply to hifi systems because it is a quantitative concept. Sound quality is by definition qualitative and there is no standard scale against it can be measured. 

Everybody’s entitled to their opinions on hifi. However, saying there are diminishing returns doesn’t make those opinions any more valid. It’s just an overused cliche that sounds impressive but doesn’t mean very much.