Quoted from ForceFlow:
Although it's a lot of fun, it isn't an A-list title. From what I understand, years ago they were so incredibly unpopular that they were parted out for their boards, which is a large contributing factor in their rarity today.
you need to qualify this with "on route"
Yeah, on route when the movie came out and was a turd, the general population did not play Congo. When the general public does not even give a game a chance due to a bad license then route operators are gonna just take the hit and pillage parts to keep other games like AFM and MM running which earned big time.
That for sure increased the rarity level and decreased the supply.
Reality is that about 10 years ago, the collector side of the hobby really started growing more and people actually started giving the game a shot. They no longer had the bias of the poorly received movie and instead just treat it like a jungle themed game with an ape. They played the game for what it is and realized it has a great layout, some really good shots, a unique style of code and some really neat toys and features.
Congo has been recognized as an A list title by quite a few for a few years now. People missed the boat because it was a "bad movie". Maybe I am crazy but I actually think the movie is decent when I watched it now. Some funny characters and good 90s cheese. Game is even better and call outs are even funnier to me.