Its value is so high because it can only be looted about twice a year per server. Required as an addon for 2 different outfits. The restriction of moving items to different worlds and the merging of worlds that happened in 2017 all contributed to making this a much harder item to get. This is what makes the item so valuable. Low Supply and High Demand
The history of the Hat itself... well monetarily it has increased in value throughout its time in Tibia, as people had more money they would pay more for it, increasing rapidly until a spawning issue in 2013 was fixed which slowed its value increase but still it increased. Then increased faster after 2017.
Non monetary wise - Its Ferumbras' hat. Sorcerer's are known for their hats. If you have his hat you killed him