I don't believe Dacs are any different to any other commodity on the planet! There is a diminishing return as you get more expensive. In todays money I don't think there is any real "need" to go beyond $2-3k for a dac and certainly not beyond $5k to get 99% of the sonic performance of something that is $20k. I honestly don't believe it is even a 5% improvement between the best of the sub $2k dacs and a dac in the $10's of k's. I think the majority of people making claims otherwise have either spent the money themselves, and therefore hear the improvement to justify the expense, or are otherwise deluding themselves. I don't have any objections to someone buying a $20k plus dac.....hell, I might even do it myself if I was a millionaire, but I really don't believe the sonic improvements are real. Sure, you might get top of the line components and finish.....but that's really what you are paying for. Dac's are no different to handbags!
I am very late to this thread and chime in only to offer a side opinion of someone who has been climbing the DAC ladder for a while and made many bad and a few good investments, so I feel I can offer both opinions fairly objectively. I haven't counted recently but I have owned at least 10 pretty high-quality DACs in about as many years, and still own about 5 at the moment, all in the $2K and above range. Many are in the $4-6K range. I stupidly suck at selling ones I'm not regularly using, although I have 4-5 systems running normally, so many do get used every month.
First, I spent $20Kish on a DAC stack (DAC + clock) a year or so ago for my primary system, and for me, I will state in no uncertain terms that it was worth it to me. I had been dabbling around in the $2-7K range and also had a disappointing experience demoing a $15K one. I am certainly not claiming to be an expert but I do have the ownership experience to feel I can offer my opinion, which can certainly be different than someone else's and I respect that fully.
These days almost all DACs in the price ranges we're discussing are "fantastic" by most standards. They recreate music very well and most in this forum would likely consider the large majority "very musical" and "highly enjoyable." They all require investments in the source which might eventually include clocks, serves/transports, cabling, network filtering, power-filtering, and a host of other expensive investments to get the best of out them. I believe we're long past the "cold/analytic/digital-sounding" DAC days if you have a properly matched DAC and the rest of your system (before and after) compliments each other as well. Your choice of speakers, amplification, source material, and about 30 other things all can affect the ultimate effectiveness of a particular DAC for you, in your system. Your preferences might have the ultimate effect on your enjoyment after all of that is sorted.
My opinion...what you might, might notice when you went to a "$20K"ish DAC is really some subtle but ultimately emotion-driving nuances that other DACs are actually missing--something you would never think to be missing until you heard it in your own system, or maybe spent tens of hours listening to music that you are emotional about in a system with such a capable DAC.
One such quality is somewhat hard for me to describe, but the front-to-back dimensionality of a particular track can sometimes come off as "flatter/less dimensional" in some $2-6K DACs, with that perspective. Those DACs can still have a phenomenal side-to-side and top-to-bottom, full soundstage sound that doesn't remotely feel compressed and can even come off as "massive." They will sound beautiful and musical and be worlds better than lesser DACs still. Some will even do a decent job front-to-back vs. some of the truly impressive ones. This quality is the sign of a great DAC to me, and no doubt there are some truly superb DACs in this price range. However, what you might find you are missing later is that very subtle but largely noticeable front-to-back, I can "walk around in the song" dimensionality that you would never know you were missing until you hear it in the context of a really, really amazing DAC. If you have this, and spend hundreds (thousands?) of hours listening to your favorite artists and albums and music that you are truly emotional about, taking that extra layer of nuance away later might be very noticeable.
Related, the micro-dynamics available and audible at lower volume levels is also something you must hear to appreciate and understand. A truly, truly incredible DAC (and surrounding system) can play at pretty low levels and still convey an almost unbelievable but certainly emotional and dynamic experience that you might not have felt possible before you heard it. I haven't yet heard a DAC in the $2-4K that does this as well as my much more expensive stack, all other equipment equal.
This sounds very cliched, but I would certainly recommend you try to hear an "even higher-end" DAC than what you have grown to love. I know with today's environmental constraints (covid, less local dealers, dealers' understandable reluctance to ship a $20K loaner piece of equipment, etc.) this becomes really hard to do without trusting the forums and buying one yourself, with the obvious risks in that. I am not saying you will definitely agree with me, nor that even if you hear "improvements" you will justify to yourself the additional (in some cases "substantial") costs. $20K is a really big sum of money for most--I get that--and as I said I respect that value is very subjective. I just don't feel that "delusional" is accurate for some who have done a lot of listening. The emotional impact of some of these seemingly small "on paper" nuances can be pretty intoxicating once you hear them, and could be really hard to live without once you have them.