Very. As I understand it (wasn't alive at the time) only around a dozen of each model were made.
However, it is only valuable in the right market. If you know how to play your cards right in the Mini market I could see it go for much more then the 10$ it is now (similar models of equal rarity I have seen go for around 150$.) but again, you have to play your cards right, and that isn't guaranteed. Barely a trace of this contest is left today.