What makes a DAC so expensive?

djones51, you said, "You take those top 20 DACs from the $199 Modius to the $ 11,000 Mola Mola and noone except perhaps a few young people with extraordinary hearing could tell one from the other." 

Please provide data for support of that comment. 

This has devolved into a fuse or power cable discussion. 

Obviously @djones51 is not going to change his mind no matter any one else's experience and there's no way he's changing the minds of people like me with the experience that different dacs matter and objective measurements do not predict subjective experience.

In the end we all have different ears and systems and everyone can be right.

At least discussions like these do help readers learn who's impressions they might trust. It's great when you find someone who hears like you and you know you'll like anything they recommend.

We need to stop paying any attention to dj51. Folks like him have ruined this site for good. Very sad Agon reality. Really hard to learn from the community’s combined owner experiences with various products and tweaks because we spend so much time dealing with the nonsense that derails real learning and community. This forum is all but gone for me and so many others. Start looking around and and see how most of the wise and experienced Agoners are becoming more and more silent. Many have moved on. 

Power supply filtering has a lot to due with lowering distortion 
with digital jitter,noise artifacts do matter. Even usb cables matter a lot if you have quality cables And equipment to justify the added costs for example I bought a excellent usb cable from a Final touch audio Callisto usb , that truly Improves the perspective which brings it closer to what people call a analog  sonic signature. I may not hear as well as a youngster but differences in 
dynamics,and dynamic shadings I can Clearly here the differences 
in quality digital ,we have done blind testing many times .i view my 
views on my many years of experience and testing .

How does the issue of compression figure in? Wouldn't a compressed signal result in distortion?

If it results in distortion then it is measurable. If it is above a certain level it will be audible. If it is audible then it's a lousy DAC sell it to an audiophile and move on.  DACs that are well engineered DO NOT have sound signatures they are considered audibly transparent.