Audiophiles are famous for their devotion to pure, undoctored sound, and for being willing to spend big money to hear it. But that devotion doesn’t mean that every overpriced piece of stereo equipment is worth its salt, and clearly, some companies are deliberately practicing upon the credulous simplicity of their audiophilic customers. How about $6,820 for a volume control? Or $2,100 for a power cable? $30,000 for speaker wire? Or for a real bargain, how about $200 for a CD mat that promises to “create a very specific energy spectra that mechanically dithers the laser”?