This analysis assumes that the flow of goods only ends up with the combat classes being the only consumer.
This can be broken in a couple of ways:
- Crafters and Gatherers will likely be users of materia-enhanced gear also.
- Crafters and Gatherers can presumably add AP to items as well as the Combat classes.
If Crafters are also consumers of materia, it means that they will be paying a cost for materia that does NOT get directly passed on to the end-consumer, because they are the end-consumer.
In addition, this whole chain of logic rests on the assumption that crafters can indiscriminately set their prices however they want. This would be true, except for the fact of COMPETITION. Yes, there is competition amongst crafters.
Look at this scenario:
Crafter buys semi-rare materia for 5M, adds to item, lists for 6M. Before someone buys it, another crafter buys the same materia for 4M and lists it for 5M. Before that sells, another crafter buys the same materia for 4M and lists it for 4.5M. Now, the original crafter cannot even make a profit on the original 5M purchase. This risk is in part why the markups are so high. The person selling the materia is guaranteed 5M. The crafter purchasing it is not.
Crafters are no greedier than battlers or gatherers. Everyone wants to sell their goods for as much as they can. However, the system should be a little bit more balanced.
Suggestion:
If crafters cannot create their own materia (for their own uses), then they will be an end-product user of crafter-oriented materia.
Then the battle classes can mark-up such materia as much as desired, since the cost will not be passed back to them. Further, since crafters "have so much gil", the competition amongst crafters for rare crafter-oriented materia will be fierce, and prices will be high.
The situation then partially reverses, where battlers (say), purchase gear from crafters, turn said gear into crafter materia, and sell said drastically marked-up materia back to the crafters.