All the topics mentioned above are religion, not science, unless the said cable is really crap. I have tested and measured some that are! Beyond that it is a matter of belief which is independent of reality. A cable can not add anything the source material does not have. That would be magic. Whatever makes your music sound good to you, be it science or psychology does not actually matter.
All the " I can't measure" is incomplete. As a technical non-believer, I admit this so to say it measures perfectly therefor it is the same is not accurate. Even the lead engineer for the Audio Precision tester says so.
All the "sounds like to me" has no bearing on reality either. Again, I don't dispute you do hear a difference. No one can tell you what you hear, only you. The question is why? If it sounds brighter, it can be measured. Either linear or non-linear distortion. Nothing special. If it has more "air" , that is also understood linear distortion or BW. If it has more detail, it is the other cable has masking distortion. Well understood.
I'll stick with my reasonable well made RCA cables ( good to about 50 Mhz), well shielded USB from a trustworthy supplier, generic power cords with a ferrite just for fun, and my generic 12 gauge speaker cables. If I won the lottery I would buy speakers, electronics and lots more music. I have generic CAT-5 for my network, RG-6 for my cable and antenna ( triple shielded for FCC requirements). No problems. HDMI cables are a lot more troublesome but most of that is the fault of the poor specs and interoperability testing of a terrible interface. Yea, I am not a "believer". I am too poor for snake oil when there are real sonic improvements to be made. If anyone would like to drop off a Sonas Faber Stradivari set, maybe I'll try some fancier cables. Until then, cables are below the noise level.
All modern solder is Tin/Silver as tin/lead was outlawed. If two circuits you think are the same but sound different, ( I accept your word they do) you might take a closer look. Transistors have HUGE differences, as do all passive components. Even with high levels of feedback, they can differ.