What makes a DAC so expensive?

Engineering is expensive. Parts are expensive. Manufacturing is expensive. You can go the cheap route or the bespoke route. If you really want to know why good DACs are expensive, read the reviews! 

as to what matters in a dac, let’s make this simple, even though it isn’t...

a) the digital (bitstream) input signal needs to be received and timed correctly for d-to-a conversion, so clock circuit and jitter reduction is key, this is done by electrical isolation, reclocking as needed

b) then the actual d to a conversion / filtering needs to happen with low distortion both in freq response and in timing (phase response) - this is done by the internal dac chip/circuit or discrete ladder network, depending on design

c) then the analog output (post conversion) needs to be prepared for output to the receiving device... this is done by internal amplifiers, or transformers, or some other method... very rarely is the output ported straight out of the dac chip (there can be impedance mismatches with preamps/amps/whatever device is to receive the signal to amplify to drive speakers/headphones you listen to)

d) all the above needs to fed clean and strong power so they do what they do without added noise, so internal power supply design and quality (and power supply isolation of the analog from the digital sections) is key

so when knowledgeable people correctly say, "it isn’t just the dac chip (akm, burrbrown, ess sabre, wolfson...) or the ladder chip (philips tda, etc etc) or fpga (custom circuit) that makes a difference, it is the IMPLEMENTATION of it", that means ALL THE ABOVE designed and working in concert to produce good analog sound, as a holistic system

’what goes into a dac to make it good’ class 101 now in recess

hope this helps

@jjss49 Thanks for the short course! Your information is helpful!

A) Clocking and jitter have been teased out fairly frequently, in my looking about. I know you can buy external re-clockers and spend thousands doing so. 

B) Schiit claims in their rendition of Multibit, or True Multibit, a "time-and frequency-domain optimized digital filter," but I couldn't begin to make sense of it...

C) This notion of output being "ported" out of the DAC chip is fascinating. Perhaps there are a variety of ways of achieving this, perhaps with some Mundorf opulence? I jest, but it also intrigues. . . 

D) The Allo DAC I mentioned made it clear that management of power is a big thing. I wonder how they pull it off with smaller DACs, like the Schiit Modi. 

I have the Modi, presently, and I'm curious about a higher end piece, but I'm struck by how well it fits into my system, not infrequently producing 3-D images from good recordings, and accurate tones in most places, perhaps a bit bright here and there, perhaps a lil under-developed here and there, but perchance this is also partly the fault of the recordings...

Whether it's a DAC or speakers, when comparing two good alternatives, I doubt most of a big price difference is in the parts.
Many high-end products are built more or less to order in small numbers, for affluent customers willing to pay a big premium even for relatively small differences in SQ. The company may not be over-charging for its product.  It really does cost more to make, deliver, and support it. But not (primarily) because they use vastly more expensive parts.

Recently I looked at Devore speakers. $8400 for the O/93, $12K for the O/96.   Plenty of decent, 2 way bass reflex boxes are available for far less. Devore uses veneered plywood baffles, not MDF.  Sure, veneered plywood is more expensive, but not THAT much more.

If you’re using a Schiit multibit modi try the Modius you might notice a difference depending on your other components.