http://www.audioholics.com/education/cables/top-ten-signs-an-audio-cable-vendor-is-selling-you-snake-oil Interconnects represent the simplest component in the A/V chain and possibly the most hype. Personally, I don't use lamp cord wire and I am not a diy'er so I will pay a reasonable amount for a cable that has quality connectors and a sensible aesthetic appeal but $21,000 for Audioquest Everest speaker cables is beyond ludicrous in my opinion. There are a plethora of other preposterous examples and I will leave that for the reader to explore. However, before moving on, I would be remiss if I didn't share this:
http://www.instructables.com/id/How-to-make-a-Transparent-Audio-Reference-XL-Speak/#step1
Lets talk speakers. Stereo speakers determine the overall sound quality of your stereo system more than any other component providing you have purchased components that meet the criteria I outlined above. Speakers are the final frontier between your system and your ears. Speaker specifications are not enough to determine which speakers will provide the most personal satisfying listening experience. I suggest reading: eCoustics.com - Understanding Frequency Response Again, you must trust your own ears. I can't overemphasize the importance of auditioning as many speakers as possible and ultimately deciding on those that deliver the musical message, without fatigue, naturally to your ears.
Finally, the scientific basis of the interplay between human hearing and the brain is nebulous at best and possibly explains why individual listening differentiation exists. Understanding and applying the scientific side of audio fidelity, auditioning and trusting your own ears, and a modicum of common sense when purchasing high-end audio components will insure one a salient sound system and indubitably save one some dollars to buy some "music" to hear it.