My hypothesis is that the $1000 cables help sell the $300 cables. I’ve seen comments to the effect of: “I’m not fooled by those $1000 cables, so I saved my money and got the $300 cables instead.”

In other words, they got fooled.

What’s happened in electronics is that there’s a cutoff, above which the audio quality doesn’t get any better, but that cutoff is much lower than anybody can believe. So the psychological cutoff is higher than the physical one, and a role of marketing is to raise that cutoff even further.