Peregrine makes the point of:

If the warrior does ALL the work to get the materia why does he have to pay a butt load of gil (making the obvious assumption that crafters will overprice as they already do) to infuse the materia into his new weapon.

AND

Said crafters will be able to craft the items that the warrior buys (that is +1 Crafter -1 Warrior) assuming that most crafters will want all the mats to be provided by the warriors, the warrior purchases the catalyst (that is +1 Gatherer -1 Warrior) now the crafter also has a fee for doing this for the warrior (that is +1 Crafter -1 Warrior) Crafter infuses the materia on the new weapon, rinse and repeat.
All in all you have Crafter+2, Gatherer+1, Warrior-3.

His point is a completely valid; the combat people will loose out in the long run and the Crafting classes will end up controlling the markets without any real need for checks and balances.