What makes a DAC so expensive?

No audio equipment is 100% transparent to the human ear, not the recording studio equipment, and not the playback equipment.

You really think the output stage has no effect on sound, maybe you should just stick to an avr with good measurements.

To me, in order to get guitars that sound like guitars then the DAC does not add or change anything when it reconstructs the waveform. DACs that are capable of doing this can be bought for a few hundred dollars. Some like DACs that deviate from this by playing with filters or adding and changing things that do not adhere to the sampling theorem and that's fine but don't claim they are transparent DACs or better because they can create a "sound.                                                                    

All dacs use filters of some sort, so your $200 dac has a filter. What your $200 dac doesn't have is a good power supply or a very good output stage. Most cheap dacs use an opamp output stage, which in my opinion compresses the sound.

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
I hate to break it to you, but no audio equipment is 100% transparent.

They aren't even audibly transparent.

Mahgister I agree some are more transparent than others, sometimes the ones that measure great sound like hifi and not like real music and some that don't measure as well sound closer to real music. I do not believe the measurements we currently use are always an indication of how something is going to sound.