I figure a better system would be if the crap we grind on all day actually sold. Materia is SE's first stab at that kind of system and I think its worth trying over the OPs suggestion. Not that the OP is awful, I just think other options are better right now.
Off topic: It would be neat if NPCs would resell the stuff we vender to them for the same price. Would make me feel better about all the ore and pelts I've been to lazy to retainer up. Plus I think people would get a kick out of walking up to an NPC with new stuff on it all the time for cheep.