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

Having spun an Oppo 105 for many years on its own before adding a Schiit Gungnir (bought for a generous steal from a wonderful seller here), I was immediately struck with how much more presence and detail the Schiit added to the Oppo's presentation. 

That Gungnir, even new, pales in comparison pricewise with 4 and 5 figure DACs I see for sale here.

So what do those much more expensive DACS do for sound? I mean, how much more information can be dug out of the digital files? Is it akin to what a good phono stage can do for a cartridge?