Yea, the best cables can cost $30 at least. Go all out for Mogamni and maybe $100 a 1M pair of RCA WBC's from Amazon. But plain old Belden "Brilliance" stranded RG-79 is just as good. Blue Jean will assemble cables to your length using good stock and ends. Or you can "tune" your system with boutique cables that filter and distort the sound to your liking. If you like them, fantastic as liking your system is what is important. Your system, your ears. But we do live under the same laws of physics. I don't deny differences. I have had some exotic cables and listened to quite a few in systems that have sufficient resolution. I disagree with what the differences are and why.
I have heard half-a million dollar systems. Nice. Irrelevant. I am a retired Civil Servant, not a Greek shipping tycoon. My system costs less than my collector car. The room is far more important. Actually I have been very disappointed in most boutique level systems. A prime example was the first few generations of Wilsons. They have gotten a lot better though. Current B&W are to my ears, horrible. Plain horrible. Moving way down the scale I find the SF Luminas smoother than the Sonettos. Played only at low or moderate levels of course as they are small bookshelves. Evoke Dynaudios over the Special 40's. I know, not high end, entry but my point is cost does not dictate sound. Engineering does.
OK, fancy phono cables. Exotic mono-crystal silver? Feeding what? The impedance matching RESISTOR network in your preamp! Did you modify your preamp to match your cartridge? Makes a really big difference. Even my old Hafler 101 had a pack of resistors. ( required "tuning" for phono systems) Pre to power: Uber cable feeding what? A 22K Ohm resistor. And let's not forget the RF filter at the input. I expect your amp is at least DC coupled so no electrolytic in series. They are quite audible and measurable to boot. 😁
Believe what you want. I believe my ears and the laws of physics equally. I do understand traditional steady state measurements do not describe musicality of a system. I understand the pure tone psychoacoustic testing does not describe how our brains interpret what we hear, only thresholds in isolation. Every audiophile I know understands that as does any competent engineer.
Instead of spending money on magic, I would rather see actual research done on what does make things sound better to me and to you. For real. Better HP crossover to your mains to reduce IM at moderate levels? Higher output transistor redundancy to improve transconductance linearity? Or maybe it is back to harmonic distortions masking noise floor pumping and non-harmonic problems. All real, demonstrable problems. All have real engineering solutions. Sure, in an AB test, we can identify very small differences in linear distortion, but in isolation, how long does it take our brain to ignore the imperfections? Not long.
You talk of system synergy. I agree. Due to the lack of agreed standards and the few that are at least published, we do suffer from some incompatibilities. Stupid low speaker impedances as an example. Different input impedances so as to make a passive preamplifiers a nightmare. Even agreeing on 0 dB levels is not followed. Worst of all are mastering standards not followed so as to fight the loudness wars causing digital filter clipping in our DACs. BUT, most of the "synergy" as described in ethereal terms by subjective reviewers is a mater of personal taste on what masking distortions they prefer. Do you want the detail of a Chord DAC, or the smoothing masking of a Denafritz? Maybe that new ESS but filtered and distorted by a tube buffer running class A no feedback. ( gasp).
Hearing a difference is a measurement, just as yet not always quantifiable. Measurable technical ( we hope) or psychoacoustic? Of course a lot of synergy descriptions is cut of whole cloth to sell You-Tub advertisement kickbacks.
Opinions are fine. Enjoy your system. Fall for placebo if it makes you happy as it is a very real effect, but until we get to quantum gravity, physics is the law not an opinion. I happen to like the elegance of "string theory" but as it can't actually make a testable prediction, it is only a conjecture, not a theory, and looks like it is totally wrong anyway. I'm disappointed in all the time I spent following it, but I got over it. I got over what I spend uselessly for cables. Got over what I spent on the reviewers cartridge of the month. ( I did like my F9L) Now on to how many DACs I have to go through to be happy. Seems they have measurable flaws that have not been worked out yet. Measurable, but not the ones Amir publishes.
Don't have any Carly Simon. A shortcoming on my part. I'll order that! The best upgrade to my stereo is always more music!