Yeah there's no way it doesn't cost an absolute fortune to make a Vision Pro. The display is nuts, and if reports are to be believed, extremely difficult to make and with a very low yield. Then there's a bunch of other high tech stuff in there.
It's pretty much a polished prototype for Apple to simultaneously explore possible design avenues in the VR space, gather data on and overcome unforeseen obstacles in new VR tech and its development process, and get the ball rolling on VR software development on the Apple side.
The one perplexing thing is that right now VR has two main usecases: gaming and wanking. Apple takes a dim view of both. I think that's something they'll have to re-evaluate as they work to bring out more consumer-focused, sub $1k VR devices.