trust cable companies - they certainly know more and have more experience.
I am sure you can trust many of them, however, I would be cautious about their vested interest in selling higher margin products. And a $400 audio or video cable is likely a much higher margin product than say the latest competitively priced big ticket item such as a plasma HDTV or a speaker. Let's not be totally naive about the fact that these companies actually sell these things for a profit. There are probably very few who sell cables as a service to humanity because they "know more and have more experience".