It's this weird math thing...someone in another thread explained it, but I don't rememeber.
I guess they did it because the event commons store is supposed to be a sort of gold sink, and with the Goddess event, people got so many commons with the...gold pieces? Is that what they handed out? Anyway, it didn't do much damage to the gold levels of users. So they tried to make it so less went out this time, but I think it went to far in the opposite direction and hardly anyone got anything. XD