I believe that 99% of all systems will benefit more from a $15,000 component upgrade than a $15,000 interconnect.
Or you can add room acoustic treatment or a better house with a more suitable room to that list - I agree wholeheartedly.
IMHO $15,000 cables are nearly the most expensive inflexible (poor value) tone control that money can buy but I respect those with $15,000 Cables who claim to hear fantastic differences....so to each his own...audio is an emotional/perceptual thing; to some extent high prices provide comfort (compared to radio shack quality) that no stone is left unturned...no compromises allowed.