Has anyone made the jump to $uper High end and were disappointed?

The point of diminishing return is a moving target. Depends on the amount of discretionary funds available, and knowledge base acquired by the person developing the system. 

Those with a deep pocket and a shallow knowledge base are more likely to end up with an expensive system that could easily be bested by a lessor expensive one.

A large component of the knowledge base required is to understand what one's own preferences are. This takes exposure to many systems.

My discretionary funds are limited, my knowledge base not near the point of diminishing return.

Re: Law of Diminishing Returns
Just to chime in on the subject of diminishing returns, I don’t actually believe there is a Law of diminishing returns for audio, there’s no hyperbolic curve, or some artificial ceiling that cannot be surpassed. "I don't think it's worth spending twice as much to get only the last 5%." 😀 What is required is thinking outside the box. Audio is an art as much as a science.

There is also the principle of "stove piping" involved here I suspect, where audiophiles develop their systems more or less in a vacuum. And each person reaches certain conclusions based on what he finds out. Each one declares he has found Audio Nirvana, yet when an independent observer listeners to those systems he discovers that they don’t sound nearly as fabulous as their owners claim or believe. In fact, by and large, they frequently sound quite bland and generic and distorted. You know, kind of like those big expensive systems like at big audio shows.

"Wow! What a view, I never thought I’d be on the summit of Everest!"
"Calm down, were only at Base Camp. We’re only half way up."

Yer a stove piper
Stove piper, stove piper, stove piper, stove
Stove piper, stove piper, stove piper, stove

Another thing I want to bring up is there is typically a dissonance between system improvement and musical enjoyment.

And this has financial ramifications also.

Yes you can buy the best amp and you might have a better soundstage and imaging, but does it actually get you to listen to
more music longer and more frequently?  Or is it just another data point you are trying to reach in systematic improvements?

Sometimes I have to catch myself, wait, I'm spending 17k on an amp.... Am
i gonna be listening to that much more music?

while I have heard less expensive systems that sound great and expensive systems that sounded very not great, very expensive systems that were very well matched, both to equipment and room, sounded way better by far...