goodman,
I'm not sure if there is any real "difference" other than maybe materials used to build the cable, maybe some shielding, but the $30 cables do work. I am using component video cables right now for the same thing on my sacd player. I haven't tried out anything more expensive. I am sure that there could be a bit of a difference in sound if you do indeed get better cables, but unless your source is really good to begin with, I am not sure better cables are going to do much for you.
-capT