Re: List of Alll the Key Props in Movies.
Holy cow! I didn't know props could get that expensive. For that price it better actually open the portals eh? I'd love to meet the engineer who put that thing together, see some of his schematics. How long do you think it took to design?
Yeah, it's pretty amazing.

According to the trivia section of IMDB, Richard Edlund of Boss Film Studios (now defunct) made each of 3 working props.
The only other info I could dig up is below:
from he-man.org:
The Cosmic Key was the most complex prop produced for the big screen version of Masters of the Universe. Billy Barty, the dwarf actor who played Gwildor, would ‘play’ the Cosmic Key as a sort of technological, yet seemingly magical musical instrument as it would instantly open a dimensional portal to anywhere in the galaxy. When he played the instrument in the film celestial music would emanate as its arms spread open and spun around while numerous lights blinked. The piece stands 20 inches (about 51 centimeters) tall and is constructed of steel, aluminum, brass, resin, and filled with motors, gears and motion control electronics.
Richard Edlund, who was head of Boss Film Studios, was contracted to make most of the props in Masters of the Universe as well as create the visual effects for the film. Edlund states this highly complex prop cost more than $150,000 to create and since it would sometimes malfunction on set, he had a “Cosmic Key Team” on hand to make emergency repairs and adjustments to ensure its proper function.
from IMDB:
A total of three working Cosmic Key props were built for the film, each personally constructed by Richard Edlund. The props were extremely fragile and broke down easily, so a special team of prop technicians had to be on hand at all times to repair damage during filming. As of 2012, they are valued at $6,000 each.
There were a couple of toy versions released which are as close as I'll ever get to having one, I think. One of them went along with a mini-comic that was published around the time the movie was released. It's the typical He-man bendy plastic, but it's painted to look like the prop from the movie. The other is quite big, almost 4" tall and is painted to look like the mini-comic version.

And now I have to go and watch the dang movie again! :lol