The center image thing you mention must be specific to your system as I LOVE the Hero XLR’s Perfect center image wide and deep soundstage, neutral tonal balance powerful bass reproduction.
In my experience with a pretty revealing system, the single biggest benefit with cables is making sure all cables are XLR and all components are fully balanced. Once you do that, the difference between one nice cable and another is a lot less noticeable, to the point where a reasonable low 3-figure set between the pre & amp, and dac & pre works beautifully.
Another big one for me was keeping the speaker cables as short as possible by getting the amp or amps near the speakers, and running longer XLR runs to the preamp if necessary. That’s far more desirable than running long speaker cables in my experience.
“I have no idea why anyone uses them”
Rightness of tone and timbre, less “tizz” or edge/transient distortion that you may not have realized was there until you didn’t hear it; Instruments and voices sound more like instruments and voices…
And no - it’s not reasonable economics. A $500 cable is not “25x better” than a $20 cable. More that it is possible that it can do some things the $20 cable can’t. More like “x% less bad”. X% more information gets through to the next component. X% greater synergy in your system.