As an analogy, you can buy a $300 digital camera to take pictures with a run of the mill plastic lens. Or you can buy a $8000 Leica. The difference in quality is obvious to my eyes. But if you don’t care about image quality to that extent, save your money. Go el cheapo.... Just as with cameras. The world’s best photographers shoot with Hasselblad and Leica for a reason.
Actually I think this is a bad analogy. The analogy between camera's (sight) and audio-gear (sound)
Everyone can quite easily see what the 'sharpest' (best) picture is.. there is no question about it in most cases. Either something is sharp, completely in focus or it's not.. This is either due to the technique being used or because of difference in equipment (sensor size, lens, resolution). Colours and everything else can be adjusted and tweaked to anyone's liking in post.
Now, sound (music) is much more ephemeral. It seems more a thing of taste, nobody can say or declare : this sounds best because of this or that.. everyone thinks/hears something different. Making things even worse. The space you are listening in even determines the sound you hear, probably to a greater extent than anything else. So even the 'best' system (whatever that may be) can sound worse than the worst system if you are listening in a cave... a picture is the same everywhere, unless ofcourse you turn off the lights.
Sound seems too subjective.. just look at all the reviews.. how fluffy can it get... pages of pages filled with fancy words and actually saying nothing. The truth is in the eye of the beholder.
I've personally tested numerous DAC's ranging from a few 100 $ to 10k and I can't really hear much difference.. on the other hand there are those who claim to be in nirvana when they hook up those new 20k interconnects and a magnet here and there an all is well :s
PS You say that it's easy to tell a camera system of let's say 20.000 dollar apart from a 2.000 dollar system. I bet you, it's not.. certainly not when it's printed. I'd even go as far as to say that a picture taken with Canon 5D camera (with decent lens) a camera from 2005 btw is as good as a the same picture taken with a recent 20k camera-lens combo. There is of course much more to a camera than the image quality alone (other features, size, sensor size, resolution, build quality, frames per second, brandname...all adding to the final cost of the product)
So maybe, it is a GOOD analogy after all! all DAC's sound basically the same but the feature set is different, a bit like comparable camera's have comparable IQ. In DAC-speak :If you want a special implementation and you don't want a chip DAC.. well then the DAC will be much more expensive.. will it sound better? that's up to you...
PPS Funny you mention Leica, because 99,9% of pro's don't use it... why? cause it's not suited for the job (in 99,9% of the case) there are of course the exceptions