Quoted from lordloss:I can explain this.
Collectors of any type LOVE making lists. When games get too spendy, they find ways to be happy with other items. So they start a topic and ask "what are the hidden gems of pinball"
Since they can't/won't pay for AAA games like MM and AFM, games like congo get brought up because they were $1500 and better value. This leads to more exposure of not as great games and starts driving the price up. Eventually they almost talk themselves into believing these are amazing games.
LOL, Congo was always awesome....people just didn't want games based on movies they thought sucked. This is why Shadow, Congo, Dracula, etc remained "cheap" for a while. As prices went up, cheap become more enticing, and then people realized "oh, wait - yeah, this theme sucks but the game is super fun!"