Like most Pokmon cards, the value of Raikou depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Unseen Forces)
Every time you proliferate, your walkers gain loyalty without activating abilities, pushing them closer to ultimates the moment they enter play
Sure, a Drannith Magistrate is about as safe a stax piece as they come, but land an ill-timed Teferi, Time Raveler and suddenly you are the only player capable of holding back the bevy of opponent win attempts which may be made as the game progresses
As players digest the new Edge of Eternities spoilers, the secondary market has reacted quite strongly to them
And it gets even worse when you start comparing the SR POPs to the FA POPs within each set - few sets have close to a 2:1 ratio of FA:SR to reflect the different pull rates between rarities