I don't think I'll ever be a believer..
Anything audibly different is measurable, speaker placement, DACs and Amps are all able to show their differences measurably (see all the lovely graphs around) and even then you can argue over whether you can discern those differences (Some people may well have golden ears)..
I've tried bi-wiring and bi-amping on my old B&W Setup and it was obvious it wasn't going to make a blind bit of difference.. We had friends around doing blind tests and none of use remotely guessed either, that includes swapping the QED speaker cables for mains cables..
I'm sorry to say in this case it is clearly placebo because of the obvious differences touted, and I am OK with placebo..
My headphones aren't the best, but OK (Focal Elegia) and like other headphones I find almost every day they sound different, some days a bit crap, some days a bit better, sometimes they start off crap but get better as I listen to more music.. There is nothing wrong with the headphones (occurs on all my headphones), it's the variability of myself.. What I'm not able to do is perform this at will just be looking at a cable or similar..
But there are definitely a few people that can simply set an expectation that for them is absolutely 'real' and they suddenly hear something different.. it's been borne out via double blind testing time and time again..
The only issue IMO is if you start pushing this on to others.. Be happy that you perceived huge differences that make it more enjoyable to you, but you are in a very small minority and it's disingenuous to tell people to spend money for improvements they are highly unlikely to experience.
I almost admire people that can hear the words "Halve the resistance/change the capacitance" and immediately set a huge expectation of improvement which they instantly hear, all I see is halving a tiny value that compared to the load is several orders of magnitude less and expect it'll make bugger all difference that would not be measurable unless compared to a wet piece of string and lo and behold I hear no difference.
I do get that sometimes nay sayers cling equally to incorrect scientific assumptions, such as only ever looking at frequency response as the only measure of audio (very misguided) and can over simplify things, but 99% of the time the sentiment is correct.. There are some clangers though, people clinging to 'digital' must be perfect forget there is a temporal aspect to digitial signals and their presentation, especially compressed audio and famously it has been easily shown the effect on the output when clocks are incorrect etc.. Not to mention analogue biasing/colouring from any DAC.. HDMI is the most disingenuous, the only way anyone has been able to show a difference is through deliberately gimping the test so the 'poor' cable is just causing the HDMI to fall back to a lower bitrate, thus losing information that can be observed.. the reality is that is nothing to do with spending £KKKKK's on a cable, just select a properly constructed/designed one that can achieve the bitrates with ease..