Dk 64 came with a free Expansion pack that worked with multiple games like Majoras mask, Hybrid heaven, perfect dark. So people bought the crap out of DK 64. If they are not reproductions then they could still shoot up in price. Kind of like when pokemon go released, the original pokemon games shot up double the price. People play the new version of the game and find out its worse programing so they get nostalgic and buy old school. As far as being $100-$150 each goooooood luck lol. Even games that are bought to speed run aren't that high. Highest 64 game i have seen in person was Majora's mas