Does a streamer do anything to the data that Tidal provides?

I agree with the OP.  Any computer can do what a streamer does.
The advantages of streamers are basically 3 fold.  First they eliminate the noise that a computer, which has many functions to do besides transmitting musical data to a DAC, will introduce.  Secondly, they tend to have software bundled in that provide easy access to what Music consumers want—Internet Radio, Organizing the Music with a software interface, and others.  Finally, they look like Audio components, not a computer added to a system.
  How much is all of the above worth?  As always, ymmv.  However, when I see 5 figure streamers sold, I can only shake my head

Great question and one I’ve been wondering as well. My thinking is aside from what the streamers actually do, e.g., receive data packets over WiFi, Ethernet, etc., I do know that the design matters and the quality of the components matter. I personally don’t have enough experience in comparing different streamers to know how much all this affect the sound quality but I would not be surprised if they did.

As long as what they deliver is bitperfect digital output (they should and they nearly always do) there is no sonic impact (nor is there with computers). That is the thing with digital, a bitperfect copy is a bitperfect copy, and you can copy it a thousand times, send it to the other side of the world and back, and it will still be identical.
Personally I do not like the fancy dedicated streamers by audio companies. They nearly always lock you into their dedicated applications, and if there is a service you want and they do not have an app for it, your are out of luck. Here using a small (fanless) computer has definite advantages, and so do streamers like Apple Aiport Express or the Chromecast Audio (my personal favourite). These are by such big companies that no streaming service provider can ignore them. The Chromeast Audio is just $35, and delivers either a good analogue signal through its internal DAC (OK for 16/44, not quite as impressive at higher resolutions, but who streams those?) or a bitperfect optical digital output up to 24/96. What is there not to like?

If disc spinners and readers, and digital cables affect the sound quality in your system (some they will, some they won't) wouldn't a streamer?