If you are still around here, I would like to report to you on first impressions from my own little tuning/tweaking experiment. Partially intrigued by this thread, I bought new XLR cables. It was at least 20-fold price difference between old ones and new ones ($15ish to allegedly $350). My new cables appeared new, but were used. There were a couple of noticeable differences between them. New ones are much more inconvenient. They are hard to bend and I had to move the rack further away from the wall for them to fit behind. They are harder to hide there, too, as they follow their own form which likes to stick to the side somehow. Another difference was that new ones look like a much more substantial product. They walk the walk when it comes to appearance. As far as sound goes, there was an impressive lack of difference. Not for better, not for worse.
I think they were worth the price for me. I had my opportunity to try for myself and, much more importantly, I bought them mostly for the looks which they do deliver better than the cheap ones. On the other hand, I bought them for the looks but find them inconvenient because they are now more visible than the old ones. I will have to discuss that one with myself or some professionally-trained expert on split-personality disorders. At least I know that, if I decide to go back to the old cheaper cables, I will not be missing anything in the sound department. Probably, others would have a different ownership experience, but this is mine.