I think increasing synthesis yield is a good start, but also another option that could be nice would be to place a Less efficient crafting npc(s) somewhere(s). Im thinking if you can provide say... An ingot(Or lumber) and the appropriate other materials, they exchange it for half the number of a normal quality synth of X ammo. Like if turning in the materials to normally make 99 adaman bullets, instead the npc takes them and exchanges them for 50 of said bullets. Im not sure this is the best option, just brainstorming.