The irony is, that once you have the materials for better stuff, copper is basically useless and you'll still be up to your ass in it. I obsessively mine every piece that I see of course, because I could always sell it. Does raise the question of why I can't just mint my own coins with the stuff. It's not like there's a treasury or anything. Not to mention I built the fucking town, so these guys should take whatever I call money and like it.
Economics 101: I house you, feed you, defend you from hoards of monsters, and there is nobody else in existence that can do the same. See that minishark? Give it to me, now.
I suspect this hole in the game's logical presentation is going to turn up in Redigit's suggestion box a lot. It's bad enough in most RPGs, where you are single-handedly saving the universe from prophesied evil, and the townsfolk don't so much as cut you a price break, let alone give you any gifts or send people to help. But when you have summoned residents to a civilization that you literally crafted entirely with your own blood, sweat, and tears, you'd think they'd show you a little more gratitude than the availability of their services, and that you'd have some level of control over the goings-on of your fortress-town.
Then again, who am I to say? I mean, you can't craft dynamite and miner's helmets yourself, that technology seems to be lost or far away. Maybe the merchant has to hoof it over a slime-infested countryside (when you're not looking of course) to wherever you both came from to purchase his stock, and understandably demands something to make it worth his time, besides a defensible shop (that Demon Eyes keep getting stuck in).
If anything, one of my biggest requests would be more NPCs. Like, farmers for a food supply, so the other guys will show up or be available more often. Better yet, guards to keep the place safe, so I don't have to roleplay Superman in the World of Retards every time the moon turns red.