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

I think there is indeed a point of zero marginal returns, and that point is lower than many here are willing to accept. The only component that really makes a big impact on the sound and is also expensive is the speakers (and their interaction with the room). I am not the only one who will argue that Quad electrostats are the best money can by, although probably best extended with a pair of good subwoofers and room equalization (the room is the elephant in the room). Alternatively, and particularly if you need more dynamics in a large room, the Harbeth M40.2 is in that same league. Both are also highly regarded by professionals.
Contrary to what many here believe there is no evidence that ultra expensive electronics have anything to add (let alone cables). Even very affordable amplifiers have a S/N ratio, distortion and flat frequency response that is demonstrably better than human hearing acuity. In fact, quite a few boutique electronics may be expensive but measure a lot worse than affordable mainstream products (see the sometimes horrifying measurements in Stereophile of exotically priced gear). And if you do not want to believe measurements, there is also the listening test, if done properly, with carefully matched levels (within 0.2 dB and hence with amp output measured with a good Volt meter, instant switchover, and double blind). Proper methodology is crucial here, because expectation bias can all to easily creep into casual observations, however well intended. Such tests too demonstrate the folly of spending big money on electronics.
I know this site thrives on the restless illusion that somehow magic improvements are possible and require constant upgrading, but the sciences to understand this are psychology and busines economics (how do I persuade unsuspecting consumers in a market of monopolistic competition between homogeneous goods), and not physics.

The crux of the matter will be if they are willing to submit their casual observations to the rigours of scientific methodology. I do not doubt that they genuinely believe that they hear the differences that they hear. The question is whether they can make this stick under controlled conditions. I once did submit myself to such a test, believing I would be able to distinguish between some quality but not exotic amplifiers. Just like everybody else, I could not. There have been many such tests, and they all produced the same result. It is a sobering thought, but also a cheerful one: good quality audio is affordable for many. Socially and culturally we can only rejoice in that.
The only expensive component is the speakers, and the reason is not hard to fathom: they operate on the interface between the electrical and the mechanical, and that is far more complex than designing a straight wire with gain. Just look at the measurements for distortion and frequency response and compare those with the same measurements for electronics.
Moreover, even good speakers have to play in imperfect rooms. So compare their response in an anechoic chamber or the open air, with their in room response, and you can see that you have your job cut out.

To follow up on the last two posts. My recent upgrades have been cheap and made a real difference. The first was when I had moved from my Quad els57 speakers to the less efficient 2805’s and in a rather larger room, and my old 2x45 watt Quad sounded strained at higher levels. So I replaced it with a completely refurbished 2x140 watt Quad 606-2 bought for about 350 dollars. At low levels there was no difference, but at higher levels the sound was obviously cleaner and less strained. The second upgrade was when I was disappointed with my new B&W PV1d subwoofer: it sounded woolly and did not integrate well with the electrostats. So I added a cheap DSPeaker Antimode 8033 room eq unit, and the woolly slow bass suddenly became tight and clean, and perfectly integrated. Finally, last week, I decided the Harbeth P3ESR speakers of my desktop system in the study were suffering from too much bass boost from the desk. I measured them with REW, created an equalization file, and downloaded that into the Equalizer APO/Peace software in the desktop computer that I use as a source in the study (it is on anyway so I have no need for anything else as a source - rest of the system: ODAC usb dac, Emotiva Control Freak volume control and a refurbished 2x100 watt Quad 405-2 power amplifier). Here, the only outlay for obviously cleaner sound was some time spent, and the result was far greater than I could have achieved with better electronics, let alone cables.

However, the argument here is whether these high priced units are actually Porsches or just Honda’s in fancy dress, or even Lada’s for that matter. To be precise, the latter is actually my view on a lot of audiophile gear (esp. vinyl or tubes).