You guys just keep arguing between yourselves and ignore when I make a valid point against it.

First of all all shards are lv1 and can be gotten naked with the lv1 tool so in terms of repair cost these should be ignored. HQ turnins for lv45 leves are worth 2000-4000 gil depending on how many items are required. Giving 12000-24000 gil a day with negligible repairs for the synths. Even with the material gathering repairs included the result is a lot positive gil. Many of these leves are very simple and require around 15 hits on gathering and around 5 synthesis. Gatherers also get gil positive leves. This gil bleeds onto the battle classes as they interact with the market selling things they need (like items dropped from monsters or materia).

Battle classes can further compound the speed which they can get the minted crafter/gatherer gil by wearing sacrificial gear that wont need to be repaired much since the goal is to turn it into materia and sell said materia.