Great topic!
Video streamers cost less because video streaming is a big thing. The money is in streaming video services not in the streamers themselves. Video streamers are a mass market commodity that opens the gateway to making money via streaming services.
Nobody needs an audiophile streamer except audiophiles who always seek the best with cost less of an issue.
I stream mainly from a meager Roku stick in my family room system. I use Plexamp, AirPlay, etc. It sounds extremely good. Close enough to my main system that is more geared towards hifi that I don’t really care that the Roku also does much harder hi res video streaming as well for well under $100.
So hifi streaming is a bit of a racket I would say. The evidence is in the comparatively low cost of high res video streamers that, oh, just happen to also do Good old fashioned 2 channel digital stereo. Yay!
It’s just not that hard to do right these days if you make just a few right choices. Getting good sound with amp and speakers is also easier but that’s where one should look to make their big investment in good sound IMHO. Features is the thing that mostly differentiates streamers IMHO. That and the DAC for the sound quality, if that is even part of the package.
Also the underlying technologies that enable higher res digital streaming services continue to evolve, so nice to be able to keep up with those. Another reason to not invest heavily in any single streamer.