The Glowing Black Stone was the first item in the game that I ever saw being auctioned for 10,000 pp. That just left me slack-jawed. Of course, at the time, I couldn't imagine ever HAVING 10,000 plat, much less spending it on one item.
I suppose it's an interesting lesson in EQ economics to consider that a Stein of Mogguk is a better item to equip -- more INT, better additional stats - but the Stein is a whole lot cheaper. The only thing the GBS has going for it is that you can hold it in your primary hand and still equip a Stein in your left.