This is one of the most powerful monster cards released in the Alpha printing so its rare to find a copy that hasn't sustained damage due to heavy play. According to PWCC, the figure makes Lord of the Pit the second-most valuable Magic: The Gathering card after the Alpha Black Lotus
Gallade ex can easily knock Arceus ex out if it is already set up with three Energy, while Marshadow can OHKO it if a Pokemon was KOd the previous turn, and with the use of Red
It provides Pokemon with two Colorless Energies, potentially giving a trainer a colossal advantage in battle
Even if the Saheeli Rai has been on the battlefield a few turns and has enough loyalty to survive a Shock immediately, after the Guardian Flickers the Sahelli back onto the battlefield, it will no longer survive the Shock, which makes having access to the red instant at all times vital
People just genuinely love Gengar, and that love has kept prices strong for years
Chocobo Camp There is little drawback to using Chocobo Camp over a Forest