Is it possible to find a good DAC for under $50, 000?

OP "...It’s about whether there is a point at which sensible effects cannot be discerned."

Good question. Not in my experience. I have heard well set up systems at price points out to the stratosphere... they are all very distinctive in terms of many variables. If assembled by competent audiophiles the sound directly correlates with the sound quality.

The trained ears / brain are capable of incredible differentiation of sound qualities. Audiophilia is about pursuing perfection. While the refinements may seem small, the overall impact is significant as music is nearly infinitely variable and complex (compare to a single tone).

I just upgraded to a Naim NP555 with its corresponding 555DR PS power supply. While it did not reach the dollar threshold of the unit in the video, it was a big acquisition for me. I could not be happier. My Cary DMS-600 was an excellent unit, but the Naim has shown me what I had been missing. The extended dynamics, detail, and soundstage are staggeringly good. I'm a hard core vinyl guy, but this is very nice.

Late to the party here. JMHO-A $50K DAC would most likely be surrounded with similar priced electronics, cables, speakers and a room with treatments. Therefor it is very likely that the sound quality would be more easily distinguished. So for that person it will be likely worth it to them. 

Late to the party fthompson251, but that's a very important point. I made the assumption that the rest of the system would be highly resolving, but it's certainly possible with a system of less resolving components even an audiophile with developed hearing could miss the value of adding a 50K DAC. Great point! 

No, I don't think you could get a good stereo dac for much under $50k. But you might be able to talk Esoteric in to selling you just one of their monoblock dacs so you could have decent mono sound for well under $50k. They sell the stereo pair for $55k.

https://www.esoteric.jp/en/product/d1x_se/top