Something like a npc buying event would be good..
Helps to clear out the trash in arena and help everyone make some gold...

Essences and sparks are usually the best ways to make gold in the game.
Both are no longer useful after players reach level 50 and have maxed their dragon and spells. So, something in this direction - say perhaps a monthly or two-monthly npc who buys a limited amount of essences from players for a good price of say 90c ea?

Professions are not a bad way to make gold, but everyone is too busy into using it and hence making much gold from it is impossible unless the player does professions for money making alone :(