I disagree. IME there's a large range in cable performance and it's not entirely subjective. Either the cable smooths out detail or it doesn't, this is clearly audible. Either it has noticeable sound signatures caused by artifacts and distortions to various degrees or they're not audible. These things can make or break a system, and is often the difference between an ordinary flat-sounding system and one that immerses the listener in sound and draws them in. Cables and AC power are the backbone of a system whether you're a "cable person" or not. I'd argue we're all "cable people" as they are required for the system to work and the cables are making a huge difference in what you're hearing whether you want to admit it or not.
I do think that all of the systems that I have heard that are wired up with lamp cord or similar product have a very definite signature...one that is clearly veiled and undefined. Could one wire up ones high end system with lamp cord or similar and save a lot of money...sure. BUT, the results will speak for themselves, imho. I have actually heard a few high end systems so wired, the owners always felt that the sound was very good. Unfortunately, I knew that the system is leaving a lot behind...and could be vastly improved. I'm not saying that all "pricey" a'phile cabling is great, but the vast majority of it is superior...at least to my ears, to lamp cord...or Radio Shack special!