Back in 1.0 there were 2 achievements for gaining gil. One was the Honest Gillionare series which counted gil earned from all kinds of leves. This one is still in game.

The other one was the Dishonest Gillionare, which counted money earned from killing mobs (only humans and skeletons dropped gil). This one has been removed and relegated to Legacy. Probably because most human mobs only seem to drop a measly 1 gil each. However with the advent of gil drops from mobs in high level dungeons, this could be a fun achievement to add back in!