At HiFi Klubbben in Lillehammer, Norway some guy tried to sell me gold cables, because the sound quality becomes so much better with them. I worked as an audio engineer at the time. I just smiled at him politely, then I left the store.
Next time I came around, he tried to sell me this CD player with a huge brick in it. "You get much better sound quality when the player has a brick in it," he told me. So I answered, "For sure! It makes the sound a lot more stable! Badum, tsch!"
To be honest, cable quality do absolutely make a difference. Buying a crappy RCA cable from a third-party seller on Amazon vs a good quality one (we're speaking maybe $5-$10 from a reputable brand) will make a huge difference. Above that price tag sure, nothing changes (except if you have very long distances e.g. >5m cables where it could matter IIRC)
It had serious problems (randomly stuttering image and failure to transmit HDR). The signal test in the TV confirmed it had to be replaced. Chinese no-name junk I guess. 4K 10-bit at 60FPS was at the limit for the cable, even though it said it could do 8K. Clearly not.
Definitely, yes.. particularly with HDMI cables and similarly complicated tech. But the problem is then that they basically don't work properly. The problem with audiophiles is that they think that these kinds of digital problems are like analog problems and will first affect details in the music.. like e.g. a low-pass filter would. Making the bass sound less crisp, or the violin muddy. While in reality, if you were connected directly to a partially working digital transmission system with no error correction or buffering, you would instead experience the equivalent of yanking out the cable of an electric guitar without first muting the amp input. Or the sound of throwing your hifi amp through the nearest glass door. Or at least horrible squeaks. Not a subtle degradation of sound quality for sure.
Next time I came around, he tried to sell me this CD player with a huge brick in it. "You get much better sound quality when the player has a brick in it," he told me. So I answered, "For sure! It makes the sound a lot more stable! Badum, tsch!"