Dealing with big undercutting

[Chyro]

That's assuming the buyers have no recourse but to be gouged at the marketboard. When expensive stuff is 4x production cost, it tends to not sell at all.

You'd be surprised. People that are lazy and have lots of money don't really care how much cheaper the production is, if they can just get it quickly from market board for 'cheap' in their eyes.

Silly example: Bronze Rivets! Production Cost (if buying the ingot from npc): 9 Gil! ...sells for 50-100 gil (might differ between servers). That's like 5-10x the production cost. And people buy a bunch of them each day.
(...like I said, silly example. Though there's plenty like that even with bigger numbers.)