I could bore you for hours about this. Back in the 80's through to the mid 90's I worked at one of the leading UK audiophile retailers.
We supplied the real-deal UK specialist kit that was clearly and demonstrably so much better than any high street crap - this was the time of the "stack" system - and kit by Rega, Arcam, Royd, Creek etc was not too expensive and was just really good - well made ( in the UK!!), reliable and sounded so good.
BUT - as you got further up the "Hi-Fi" ladder, the 'Rule of Diminishing Returns' certainly applied.
So, a UK seperates system for about £1000 ( eg a Rega Turntable, Arcam CD/Amp/tuner and a pair of Royd Speakers) was a world away from a £500 stacker system. Just so much better to listen to, better made, longer lasting... easily justified by any measure.
However, a £10K system was not better than the £1000 one by anything like the same degree, because the systems like the one detailed above were really very good indeed, so the next level up ( Linn/Naim/Chord/Meridian etc ) were much dearer. However, they were still better systems and ( like cars/clothes/guitars etc etc) it is the buyer who decides if that extra 5-10 % of performance is worth another 30 - 50 - 100% or more in price.
The ''accessories' are where the snake oil and smoke and mirrors kick in - for both retailers and hobbyists ... and I admit to getting so fed up with it all that the "tweaking" and "mods" were directly responsible for me changing jobs🙁.
Grown men spending -literally- days on end comparing the 'sound ' of all sorts of "tweaks" may sound fun, and we were initially at the vanguard, with Peter Belt/Malcolm Steward & various other writers/reviewers/guru's coming along to show us the latest whacky mod, but after a while it got MAD... pseudo science and mumbo jumbo.
it got to be that each day was a round of fiddling and tweaking perfectly good systems with all manner of nonsense - I got bored & frustrated as, to me, it all started to lose focus from the main issue, ie for only a modest amount more than a pile of plastic crap from Comet, people could get really good audio kit that promoted love of/buying music.
B&O never really got "tweaked" - probably because it was quite an insular brand then - unique connections and not ideally suited to the "mix&match" fiddling of the audiophiles.