My two inexpensive, but very good cable companies are Signal Cable, and Pine Tree Audio. I just got three interconnects, a power cable, and high quality jumpers from Pine Tree, and they are all very good. At less than the cables they replaced, they are every bit as good. And Signal Cable made me some custom power cords, and very long RCA cables for my sub. Again, excellent quality for affordable prices.
I've never owned the real, real expensive stuff, and I suspect if I did, I'd understand why some of them are so pricey. So, I'm gonna make sure I never hear them...