The profit margins in snake oil are too high to pass up. But you have to look at the demographic that's paying for it. They've already justified dropping $50k on a pair of speakers, so buying a 30 dollar roll of zip cord to connect to their amps is in some ways an insult to their sensibilities. Plus, it just has to sound better if it costs more, right?
We know that diminishing returns hits faster with interconnects than with components, but folks who can afford it will buy it regardless. The nauseating marketspeak from those peddling this stuff certainly doesn't help matters.