When I used to visit hi-fi dealer shops, I have heard, on several occasions, the sales people say this to their customers (including to myself and I was a sucker back then) - "You have a $20K system. Why would you compromise it with cheap cables?". I later found out that the margins on cables are even higher than on electronics/speakers. And then there is the "weakest link in the chain" argument from the sales people - now that you have a higher end cable between your DAC and preamp, the rest of the chain is weak - so the customer is sucked in and then its like crack cocaine. Then there are power cords, speaker cables, etc.
Full disclosure - I once bought a $400 RCA interconnect. Luckily I was able to sell it for a decent price and it didn't go beyond that. I cannot believe I was suckered into buying it.