Seems strange because according to my physics course, what receives well emits well.
About the shielding, even if it s connected to one end, the noise will propagate in the cable and reach the other end.
I am no acoustic engineer but I think it has something to do with what they called the 'Skin-effect' in EM(or the magnetic field and current density at the surface of the conductor). Basically by arranging and twisting strands of copper wires in certain way based upon the flow of electric current, the magnetic interference of the conductors can be minimized, and hence reduces signal loss.
IMHO, the difference between a $50 cable and a $500 one is not significant enough to justify the cost. Unless you are running it across the Pacific Ocean, a decent low cost cable would do the job. On the other hand, you wouldn't want use a coat hanger to connect a CD player to your pre-amp. However, it does look kind of impressive with these chains and ropes lying behind your system.
I have one or two directional cables. As already said, the directionality has something to do with grounding and I remember doing a test to verfiy this (can't remember the exact procedure at the moment). In any case, I found the sound quality to be the same if both units connected at the ends are well-designed with proper grounding.