ive been thinking for a while on how to reduce the price of materia, and ive come up with a simple.. ( and probably incredibly unoriginal ) idea to knock materia prices and demand down a few pegs

allow the use of additional, and higher rank catalysts in the melding process

say i want to meld a rank 1 materia in an overmeld #2, this would be a 24% chance of success with your standard grade 1 carbonized matter, instead of just using a single grade one, i want to be able to use up to 3 of any grade.

using a single grade 2 matter would increase the chance by 1%, using a grade 3 would increase it by 2% and a grade 4 and 5 by 3 and 4% respectively

now this alone wont be enough to budge the prices in any fashion, hence the idea of using multiple catalysts.

each addition catalyst would increase the success chance by a percentage equal to its own rank, so in the above situation of a rank 1 materia overmeld #2 with a base success chance of 24%...

3 rank 1 catalysts would give a 26% chance (0 base increase +2 for extra rank 1s)
3 rank 2 catalysts would give a 31% chance (1 base increase +4 for extra rank 2s)
3 rank 3 catalysts would give a 36% chance (2 base increase +6 for extra rank 3s)
3 rank 4 catalysts would give a 41% chance (3 base increase +8 for extra rank 4s)

as a different example, bob is being picky and wants to meld a 5th rank 4 materia in his offhand tool.. with a base success chance of 4%

while rank 1-3 catalysts are worthless for this, bob would still triple his success rate to 12% by using 2 additional rank 4 catalysts

this increased succes chance in melding would knock down the ammount of materia consumed for overmelding a decent ammount, in addition to providing a higher demand for catalysts which currently are available in over abundance