Hey there, I'd like to suggest a change to progression. Is it possible to make newer modules still cost iron or some of the lower tier metals? My concern is this, after a while iron becomes a junk metal and it doesnt seem to be worth keeping it. My best example is terraria vs modded minecraft (in terms of resources). In terraria, I'd tier up to the latest gear, and all inferior metals are already junk. In modded minecraft, the recipies and easily accessible materials such as coal, wood, and iron, are still mostly used to reach higher tier blocks.
In this way, we would still find early metals still useful. Maybe in terms of immersion, higher tier equipment would need rare metals that alloy with iron or metals that came before them.