If memory serves me right, certain people (personality types?) are more susceptible to the "placebo effect" by nature. Unfortunately I do not think I'm one of them (I could have cured my tinnitus and neck pain by now, damnit!) but I think even I might be influenced to hear some sort of difference if I purchased a $1,000 cable. My mood probably has the greatest factor in how I perceive sound, and even if I listen to the same song twice in a row on the same setup, I'm probably going to hear things differently the second time. Your setup is an ultimate limitation, of course, I just think that it pales in comparison to your own mind. Does this mean I'm going to go out and spend $1,000 for a cable? No, but if you have the money and don't mind if an objective discernable change in the sound has ever been found scientifically, go ahead.
If a person who once believed in cable differences goes on to do a DBT and is then unable to tell a difference, is everything rich, detailed, and liquid, or harsh and brittle? Or can they still go back to perceiving a psychoacoustical difference?