How much does a DAC do the more expensive it is?

While technology may be different, DAC's do about the same thing regardless of price, in terms of specs at least.

I don't know if price is the right differentiator either.  Use your own ears to determine value, not the price tags or reviews. 

I have not explored transports with streamers...in controlled tests the Cambridge CXC was clearly preferred to the Oppo 103...no controlled tests for the 105 as it is used in my home theater, though I quickly tired of it as a streamer for Tidal...I do very much like the SACD Marantz 30n; CD player, DAC, Streamer, that I use in good quality home office system...while price doesn’t guarantee you will like any product, I do unfortunately find the gear I like the best does tend to be more expensive...though I do find Schiit products and other direct sale manufacturers to be excellent values...it’s whatever you like best and decide is the best price for you...

Unless controlled listening tests are done all bets are off

When you use your own ears to judge, the "controlled listening test" is done - All bets are on!

If it takes a controlled listening test to determine if a difference exists, then the hunt is over.  You will know when you hear a difference.  The confusion starts when the person next to you doesn’t hear a difference.  (In my case my wife).  Who is right?  Both are right.

There are some here who don't believe we are capable of doing an unbiased listening test, that we are gullible and want to waste money on gear we don't actually like...I rarely do a controlled test, but sometimes it's easy and fun...and great when results are unanimous...