If instead of getting different "levels" of resources (leather, spine leather...iron ore, shadow iron...etc.), if we instead got oils or minerals that get mixed/rubbed on/whatever...to the basic resource? In other words, instead of getting leather, spined leather, etc., you get oils that are added to regular leather to give it the properties that we know now for spined leather. And instead of mining up shadow ore and just using that to make shadow ingots, we had to mix it with regular ore to get the shadow ingots. The purpose here is to maintain the need for the basic materials. The reason for that is the stagnant economy that we see now.