Headless computers. They have been around for a while
Also something to consider. The dongle is simply a 'dummy' monitor adapter that mimics a monitor. It doesn't really do anything. There are lots of these on Amazon for about $10, but I haven't seen one with USB-C, and also there's software integration to consider. It has gotten complicated since Apple pushed Airplay (which ruined programs like Duet Display, etc), so if this Luna 'just works' I'm all for it. Duet Display has been horribly broken for a while (although it might work now...who knows).
$80 is a bit much, but wtf.
People want OSX on their iPad. Sad we have to resort to this. If you plan on going the headless route, be advised it is not a glitch free experience. A laptop is infinitely better (although, perhaps not so exotic, and in spite of the pen interface, which can be had with a variety of HDMI graphics tablets for much less money).
Not to say this isn't a way cool thing. I will buy the Luna myself. Perhaps it's not as glitchy as some others.