I'm on my second play through of Dead Space 3 in normal difficulty, having used the New Game+ option. I was just at a workbench, and saw that the Shootbanger weapon was listed for zero tungsten, semiconductor and scrap metal cost. So I built it, and then its cost changed to 620/2450/3750 for those parts. What's that about? Did I earn some kind of perk that gave me a discount? I had recently spent some ration seals to purchase the Epic Resource pack, but I don't remember that saying anything about weapon discounts.
If it matters, I'm in Chapter 7, at the Roanoke getting the parts for the flight recorder. I noticed that after getting the parts and going to the workbench to construct it, the Shootbanger cost is now down to 300/850/1350.