IMO different wire may sound different. I usually hear a difference between solid silver and copper, for instance. I also hear a difference between cotton and teflon dielectrics.
This makes it worthwhile for me to build my own cables. My main RCA at the moment is 28AWG Jupiter silver wire for signal, Neotech 24AWG copper for ground, woven in a loose 4-strand litz braid. With some decent connectors (Vampire) it cost me about $60 to make.
It sounds really good to my ears. As far as commercially available cables, I really cannot see how their wire can be any higher quality than the Jupiter or Neotech; with the exception of Eichmann connectors, I cannot see how more expensive RCA plugs would make any difference. With markup and labor costs included, the cable I built might cost $100-150 commercially (a guess, maybe more).
So from my point of view, I can't see what benefit there would be to a cable costing $1000. Yes, wire material matters, and maybe purity matters too. But really high quality wire is just not that expensive. The extra cost is just going to be snake oil-tax. In other recent threads, it seems that people assume that if you think wire and connector types make a difference in the sound, then you must be a sucker willing to pay $1000 for a cable. I am proof that's not the case. I really believe cables matter, but only to a point that is reached relatively quickly (in terms of cost).