Fixes cost of some Mecha weapons in the Exosuit Fab (#6745)

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## About The Pull Request
 Ups fab costs for the AC/10 and the Gauss Rifle
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## Why It's Good For The Game
Makes the material costs non-trivial.
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:cl:

tweak: tweaked a few things

/:cl:

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code/modules/research/designs/mechfab_designs.dm

@@ -518,11 +518,13 @@
 	design_name = "AC 10"
 	id = "mech_lmg_heavy"
 	build_path = /obj/item/mecha_parts/mecha_equipment/weapon/ballistic/lmg_heavy
+	materials_base = list(MAT_STEEL = 12000, MAT_GLASS = 4000, MAT_PLASTIC = 3000, MAT_SILVER = 1500, MAT_COPPER = 4000)
 
 /datum/design/science/mecha/gauss_rifle
 	design_name = "Gauss Rifle"
 	id = "mech_gauss_rifle"
 	build_path = /obj/item/mecha_parts/mecha_equipment/weapon/ballistic/gauss_rifle
+	materials_base = list(MAT_STEEL = 16000, MAT_GLASS = 8000, MAT_PLASTIC = 4000, MAT_SILVER = 3500, MAT_COPPER = 8000)
 
 /datum/design/science/mecha/rigged_lmg
 	design_name = "Jury-Rigged Machinegun"