I have enough background in electrical engineering to be able to say with certainty that there are several absolutely objective criteria that can be used to gauge the overall performance of an audio playback system. Criteria such as distortion and frequency response can be measured and compared with high precision. I can also say with certainty that the build quality of a USB cable in a purely digital signal path has no impact on these objective criteria once the cable meets the minimum standard to ensure that the digital signal is transmitted in the first place. Yet experts who have spent years enhancing their knowledge of audio systems are adamant that they can hear the difference when they use $1000 USB cables: http://www.hifiplus.com/articles/first-listen-audioquest-diamond-usb-cable/?page=2
Frederic Brochet's famous 2001 study showed that expert wine tasters cannot even distinguish between red and white wine in a blind taste test. http://www.realclearscience.com/blog/2014/08/the_most_infamous_study_on_wine_tasting.html Yet we have a multi billion dollar industry based on perceived subtle variations in flavour between various wines.
What is happening here. Are we humans just gullible idiots who fall for any old hype? I have in the past when felling in a less contemplative mood than today concluded as much and I have even revelled in the fact that those of us smart enough to see through the ruse can benefit from cross subsidisation by those who willingly pay extra for no tangible benefit. http://mindbendingpuzzles.blogspot.ie/2011/04/how-i-learned-to-love-expensive-cables.html
Today however I am feeling contemplative and I am prepared to admit that there is more going on than meets the eye (or ear or tongue as the case may be). That RealClearScience article about Frederic Brochet hints at the bigger picture when it points out that there is a huge link between what we taste and smell and what we see. I think it is even broader than that. We humans are complex creatures and the overall experience that we think of as tasting a glass of wine is a combination of many tangible and intangible factors.The chemical composition of the liquid features of course but so does its visual appearance in the glass, so does the shape of the bottle it comes in and the label on that bottle. The shop you bought it in, the company you are sharing it with, even the voice in your head of the expert you heard on the radio recommending this vintage: all of these factors and many more contribute to the taste experience that is a glass of wine.
I am pretty sure that Hi Fi audio appreciation has become a similar phenomenon. The perception of hearing is such an intangible and subjective thing that many tangible and intangible factors contribute to the overall audio appreciation experience. Faithful reproduction of the sound is one aspect of course but the intangibles also contribute strongly. For those who are into such things the the warm feeling they get from seeing the build quality of a $1000 USB cable actually does influence their perception of the sound.
In case you are still inclined to dismiss these intangible issues as hype and bullshit consider another much older industry that has long understood the value of the intangible: perfume. The size and shape of the bottle and the package it comes in are all unashamedly part of the perfume experience. Do you imagine you would be thanked for delivering to your loved one a best value gallon can of their favourite Chanel scent?
Aside: Several decade ago when I was a youth the basic technical issues of audio reproduction had not yet been solved for the mass market so it was easier to distinguish between Hi Fidelity and mass market audio on purely objective technical grounds. Mass market equipment had measurably bad distortion that even an untrained ear could detect and Mike Oldfield's tongue in check admonition on the album cover of Tubular Bells that "This stereo record cannot be played on old tin boxes" was not all that far from the truth. Over the intervening decades however the quality of mass market equipment has improved enormously and even relatively modest systems are now capable of un-distorted audio reproduction over a wide bandwidth at reasonable volume levels. This is one reason I suspect why intangibles have become a large part of what distinguishes high end from low end.