The signal that goes down the cable is all ones and zeroes. If the one arrives slightly degraded it doesn't matter as it's still seen as a one. If the wire is made of copper or gold makes no difference as long as it's short.
High quality cable only really help when going over large distances.
I have also heard this but when i bought sky hd i also purchased an expensive high quality hdmi lead.i first watched a prog using the standard hdmi lead then watched again using the expensive hdmi lead and i have to say that the expensive one was better albeit only slightly.
we have just been through this and my husband ended up buying a cable for �60 (rather than the �7 one I wanted to buy in the supermarket). We also have a standard HDMI cable in the Sky box so I will try then both and let you know.