@polkalover Broad generalizations such as you promote are not universally true. In many situations a power cable change makes little difference because the are problems or performance limitations in other parts of the system. As another post described extensive experience setting up an entire system for minimal noise floor, same system approach should be applied to home audio. That approach does not mean expensive cables of any type have to be used. Quality matters. Everything matters.
If one person is happy with manufacturer supplied cables - FINE. If another wants to spend THEIR money and time differently - FINE. Manufacturers are in the business of making money and staying in business. Assuming anything else is ass -u-me, as the saying goes.
NASA and the Air Force learned when first trying to launch things into space, unexpected things happened. Well designed sub-systems did not always behave as expected and failures were frequent. Eventually smart people discovered unexpected and unplanned circuit paths, i.e. sneak circuits. A sneak circuit analysis discipline evolved. Other analysis disciplines evolved that are incorporated, to some degree, in modern electrical design. However, make no mistake that cost remains the primary driver when it comes time to stop the engineers and go into production.
Does everybody need a $200, $1000, $10,000 power cable? Absolutely not. Is there a lot of smoke and mirrors justifying some high dollar cables. Yes, but not all. There are well engineered and constructed cables that will make a difference when part of a system level approach. The only universal truth is the personal freedom to make your own choice.