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
If the $200 DACs filter doesn't alter reconstruction of the waveform or cause a deviation from the sampling  theorem so that the measurements on the analog outputs are so low in distortion and noise it's not audible to humans then the DAC is doing its job properly and it's not relevant how the output stage is constructed since it's not doing anything humans could hear.
There are basically two types of DACs those that adhere to the sampling theorem and properly reconstruct the waveform. Which means the waveform going out of the DAC has been reconstructed to match the waveform that went into the ADC. The other type of DAC doesn't adhere to this basic principle and goes off creating a sound either through filters that maneuver the waveform or just out right changing it on purpose. Now one may prefer a DAC that has a sound signature but it is not a transparent DAC that is reproducing the file accurately.
I see some good points on this thread. People actually understanding manufacturing costs, engineering, etc, and seem to relaize the last extra costs exponentially more. Then I see djones as usual poo pooing anything that costs because he can’t afford it. I can’t afford a dcs stack at new cost, and also keep everything else I have. I could,  it that stack wouldn’t be much use without amps, speakers, etc etc, lol. Dosnt mean I wouldn’t like to have one if I could. 
As I don’t have access to Djones financial records, I personally would like to focus on his reasoning, which is sensible as presented. If a $200 DAC measures .0006 THD+N, are we looking at an output value and how does power supply and/or OP amp compression figure into this measurement?