I am sure that some expensive cables are fine products in terms of their longevity, build quality and materials however their qualities as a means of transferring sound from A to B are subject to the same laws of physics as the rest of the universe.
Realistically however, you pay an increasingly large amount of money for less real world gains, sound quality being the least of them. For the same amount of money you would pay for one overly expensive cable, you might as well buy a realistically-priced cable several times in several lengths and only use the one that has as much length as is required. Or go active, wireless, acoustic, etc. :ROFPMSLAMOJ: