@GrimGriefer , an attack powerful enough to destroy the dragon from first chapter in a single strike would not matter if it cannot land. His stats mean that a group of monsters can easily kill him. MPK, while frowned upon, would not get you kicked out of the dungeon. There are also players who rob low level players of their items. Add the fact that healers aren't respected and are often exploited (since most healers skill in using their class is low and Off Tank attacks occur often). So selling the staff and having the money deposited in a personal Unrobable debit account is the better and rational action to take. Keeping the staff for personal use is a delusional act since he can't ensure that the staff won't be taken away from him.
Sure having the weapon of infinity +1 at the start of a game is nice, but it is of no use if it is robbed within 3 seconds at the start of the game.
In short, the staff is a powerful weapon, but he can't ensure that it won't be taken from him. That is why it is better for him to sell it for funds that cannot be stolen from him.