There isn't really many ways to make real money in the game besides crafting or turning houses or selling materia you earn every weak, or flipping the auction house.
Chinese Farmers usually just run the same dungeons over and over for a set amount of gil with scripts. Honestly giving earning gil other areas of the game and taking it away on easily scripted dungeons would set high standards for preventing the gil inflation. For example putting gil in high end raids and making monsters drop components needed for high end gear? The monsters can only pop every so often so that would be something the farmers would have to fight real players for.
