FATEs, guildleves, and dungeons produce a tremendous amount of gil into the economy. You make far more per day doing them than you spend on repairs and the like.

People claiming to lose 2500g to repairs in crappy low lvl gear after 1 dungeon are full of shit. In blues and high lvl greens at lvl 50, it barely costs that much when my gear is completely broken after a good run of FATE grinds.