Raw material + work becomes intermediate material. Intermediate materials + work becomes finished product.
Sometimes you end up with a byproduct that is not needed, but can be deconstructed into usefull material.
Eve and WoW both have these transition.
You could expect to buy raw material, process it and sell the resulting product at a profit. This sometimes works; you can spreadsheets and blog discussions on WoW's obsidan shuffle, or the saronite shuffle.
Sometimes it doesn't work; you have farmers gathering material, and selling the resulting product for less than the raw inputs sell for.
To my surprise, Eve's basic mineral Velspar can not (easily) be refined (prospected) at a profit. At first I thought it was just me. However, I found an ore calculator that suggests that it rarely is profitable for the basic ore.
Working with optimistic assumptions : level 5 (maximum) in Refining Level, Refining Efficiency Level, and Velespar refining; combined with a large station standing, could I spin a profit? The best price in any quantity I can find is 14 ISK/unit of Veldspar, and I can buy Tritanium for 4.6 ISK/unit.
So what does my magic calculator tell me my rewards for refining Veldspar will be worth? 13.8 ISK/unit of Velspar processed.
I have been sellling raw Velspar for 19 ISK/unit.
I am still a newbie. I might be missing something (does the time cost of transporting Tritanium - refined Velspar outweigh the time cost of mining additional Veldspar?), but for the time being no thanks. I doubt I'll be refinining Velspar any time soon.