How about bringing in a Crystal lottery! An example how this could go:
Everybody* can buy a ticket for 5 Crystals! You can buy as much as you want! The Crystals gathered are given to 1000 winners, 1000 th place the least, first place the most! The developers get 10% of the Crystals gathered! The winners are announced in this forum!
What do think yout this idea?
*all the players in the world are in the same lottery shard!