Hype, Hyperbole and high price!

"All of these approaches seem valid and tend to tell more about how the purchaser views the world than about the products themselves, IMHO."

Brilliant. 

viridian..good post..the bottom line is that if a system is not resolving enough then you will not hear much of a difference, in the sound,  when trying new cables.They certainly do,however, make a difference with each change.

Uncledemp wrote,

"I read and try to learn in these forums but it is very, very difficult to build a foundation of knowledge that isn’t undermined or disputed by seemingly educated people.

I’m happy with my system- or possibly too ignorant to know the difference. Ignorance is bliss in my case, but I am still curious as to the lack of consensus regarding scientific principles."

I suspect there actually isn’t so much argument over the scientific principles although there probably is some, but the real arguments are over why a thing would sound better than another thing when the measured scientific parameters are essential identical or perhaps even not as good. There are of course other arguments in these forums with regard to many controversial devices and tweaks that seem to defy scientific labeling or characterization or are otherwise mysterious as to operating mechanism. Thus, in the audio hobby, IMO, if one wishes to trace back and find the scientific explanation in a textbook why some things sound better than others or why certain audio techniques or innovations work might not be possible. And one cannot look even to NASA, Lockheed Martin, AES, MIT or the National Science Foundation to provide answers.

Uncledemp- your post fascinated me, and after giving it some thought, my response would be something like: 
scientific or engineering training or any form of higher education for that matter, teaches methodology- how to approach an issue and ask the right questions, rather than knowing the answers; 
a lot of audio equipment is following tried and true science or engineering principles with variations and modest "improvements" that may or may not prove to be enduring or universally satisfying;
innovation can come from anywhere- conception and development doesn't necessarily require massive expenditure or white lab coats- but the adoption of new formats requires industry consensus and re-tooling or broader manufacture that does involve clout and buy-in; many of these were utter failures in the marketplace;
Why the divergence between pure science and engineering on the one hand, and the subjective audio experience on the other? It seems to me that we are, all of us, trying to recreate a sensory experience. The engineering and sciences involved are multi-disciplinary: electrical engineering, mechanical engineering and materials science, acoustics and psycho-acoustics, etc. But at the end, there is still a human, making design choices and a human making listening evaluations. 
There are people that say that two channel audio can never recreate the illusion of a musical performance, but that, and some forms of multi-channel sound, seem to be all we have to work with right now. I've always been intrigued by the history of ideas and invention; thus, my peculiar take on your post. Others may have a different view, but in my experience, I have heard very convincing sonic illusions created by the most mundane or antiquated gear or formats, and completely unconvincing (though sometimes impressive) sounds created by the most expensive, elaborate audio systems. I'm discounting source, room and placement, and dialing in or set up as well as the purely subjective aspects of listener preference. Not sure I "answered" your question, but perhaps gave the "why" some context. 

Not all engineers are created equal plus they are also just human and not perfect so that's why results will vary.