What makes a DAC so expensive?


You can buy a Cambridge Audio AXA25 25 Watt 2-Channel Integrated Stereo Amplifier | 3.5mm Input, USB Input for $225, and most DACs seem more costly. 

I'm wondering what it is that makes a Bifrost 2 almost as expensive as an Aegir and 3x's as expensive as the Cambridge product, above. I would have thought an Aegir would out-expense a Bifrost by a factor of two or three. What are the parts that make the difference? 

I'm wondering if the isolated DAC concept is one that comes with a "luxury" tax affixed. Can anyone explain what I'm getting in a Bifrost 2, or other similar product that justifies the expense...?

Thank you.
listening99
@ovinewar I appreciate your comment, concerning the division between the search for "truth" and time protected for enjoyment. More and more I see the limits of endless searching, which seems to be pronounced in a commercial culture, where our desires our endlessly pricked, to the point of inflammation.

Perhaps our thread has burned itself out... 

Much appreciation to all contributors. If you have final thoughts, please send them along... 
@mozartfan  I have a tube amp and it is a wonderful performer. I also have a class A amp and it is also blissful. My latest DAC - the Schiit Modius - is not a tube product, but it is transparent and the overall sound quality of my system is beyond anything I thought I would ever own. I may play with another DAC in the near future and I have looked at tube DACs, with a couple landing in my price range: the Black Ice products and the Musical Paradise products come to mind. Actually, the $499 model MP DAC is under redesign and will not be available until year-end, so that's not an option, right now.

Frankly, I have been blown away at every purchase from Schiit. I never dreamed their $799 Aegir would match so well with my Moabs. For people with lower a lower budget, companies like Schiit are a Godsend. 
" TUBE Digital is far superior to any DAC "
The tubes in your Shanling cd player aren't going to produce anything without the DAC that's in it