Hi Nigel1957,
Thank you for your very full response. Perhaps you noticed I had already exchanged a few posts with the OP on the thread that you linked. As that thread contains a few posts and links to my own threads on the topic of ‘cables’ I’ll try to keep this reply short…
The reason why some companies charge thousands of dollars for cables, it is simply because they can. Customers are free to choose whether to buy or not. The businesses and business models of some of those companies will have various costs. Maintaining patents has fees and is an example of one such cost. Marketing departments typically have much bigger costs. IMO this is self-perpetuating. The more (technical) BS that gets spoken amongst communities such as online social media or even HiFi forum, the harder it becomes to keep this all in perspective.
But a few of us (you included - and typically with science or engineering education and/or training) have access to higher knowledge and are perhaps better able to resist this Marketing BS. Nevertheless, even with my own training and experience I have failed and succumbed to the marketing hype with two of my HiFi cable purchases.
Regarding the Shunyata Power cable patent (US Patent No 10,031,536), this is very clear in its claims. It is simply a very fast (low inductance) mains rated balanced capacitor pair, incorporated within the mains cable structure to do exactly what it says in the patent.
This kind of capability could be incorporated within the equipment - but the manufacturers of the equipment generally do not want to give space over to that and in any case, once the equipment performs to specification, there is no need. Furthermore, if these things were to be incorporated within the equipment design then (depending on capacity) they can introduce additional potential electric shock risk under certain disconnection scenarios.
In summary:- mains conditioning is a thing, and depending on the particular mains feed involved may improve the measured performance of the connected equipment. The key question then becomes:- are these measurable improvements consistently perceivable - with experimentally and statistically valid and sufficiently representative and repeatable listening sessions?
Which brings us to your point about The Psychology of Hearing. It seems to me there have been many threads on this forum on the topic of cables (and other things) where assessors are encouraged to ‘just use your ears’.
It is perhaps a shame (and I do feel ‘sorry’ for those members) who might have missed the very clear (and correct) advice suggested by Innocent_Bystander posted over five years ago on the ‘Ethernet Shootout’ thread here.
PS: I just hope @Innocent_Bystander approves of my methods of assessment in my own experiments.