Mining can get you really valuable stuff, but how valuable that stuff is depends on two factors... what you find and how rare it is.
A gold coin will always have the value of a gold coin (only in MD, because the outer world is fucked up long ago already).
A chunk of pure gold or a uncut diamond or a shard however, will have variable value and probably will slowly settle to a fixed currency over time. I actually want to make something semi-automated to allow you to convert such valuable resources into coins! This will also train you a bit about stock market and make you understand muc