I might bit chip in here

. The Icarus is not trying to compete with Oculus to bring the cheapest immersion and there is no point even trying. The Icarus is more is about quality, comfort and high fidelity of the experience (chalk and cheese

)
Even if I would use the cheapest projectors and the cheapest projection materials the price would be still much more than Oculus while losing quite a lot of advantages projection system can have over HMD. Quite frankly if I would have to chose between the cheap projector with cheap white projection screen I think I would go with the Oculus or 3 monitors in dark room.
The projection surface has as much impact on the image as the projector and the right combination is the main thing and unfortunately making the black pearl HDR surface is neither easy or cheap. (but in my opinion the result is worth it)
[video=youtube;QWETc7sSr50]https://www.youtube.com/watch?v=QWETc7sSr50[/video]
[video=youtube;kWt0sVmDGSk]https://www.youtube.com/watch?v=kWt0sVmDGSk[/video]
[video=youtube;twP5ZIeoGxQ]https://www.youtube.com/watch?v=twP5ZIeoGxQ[/video] - the video is bit blurry sometimes as the camera is getting bit fooled about depth and focuses through the screen (this footage was taken before I enabled the VSR 6400 x 1800)