I have $40 shielded, 24k Gold plated Monster cable cables(RCA) and some ridiculously expensive Monster Cable speaker wire. I also have standard issue, super-cheap stuff.
I use the Monster Cable, because I have it(I didn't buy it) but believe me, you aren't missing anything. Waste of money? Yes. Would I buy it again? No.
Worth it to some? Maybe if you need to be told by other people you have a nice setup.
The only way I'd consider expensive cables again is if I was building a very high end home theatre, in which case the cost of cables would be NOTHING.
Absolutely useless on a computer stereo.