So, how about your game worlds? Do you spend time exploring the implications of the fantastic? Or, is your game world more traditional fantasy?
One of things that I enjoy the most about D&D is extrapolating the consequences of magic and fantastic creatures being present. Sometimes the changes that I envision are significant, othertimes more trivial. For example, I see city-states being more common due to the presence of monstrous creatures and the apparent fragility of the peasantry. I also try to highlight the use of clay jugs full of vinegar being common household items. You have to wash blood away with something acidic, denaturing the blood, otherwise you will attract stirges. Nobody wants that.
But, if "elf knives" are left over from elf-orc wars, then why aren't there more of them? After all, orcs and goblins are a common enough threat in Middle Earth that having something that can tell you when they're around would be pretty durn handy.
...
If this kind of thing is possible, then it's possible to exploit...
Someone makes the One Ring, so, now it's known that it is possible to do. Yet, no one, in all the history of the Middle Earth, thinks, "Hey, that's a pretty nifty idea - I think I'll get me one of those too." and copies the idea?
That would be what I'm talking about. None of the fantastic is ever exploited in LotR, despite it being fairly easy and/or obvious that it quite possible could be exploited.
I think that in this instance the difference is between
possible and
accessible.
Enchanted weapons are both possible and accessible in that situation. While the Fall of Gondolin was thousands of years ago, the techniques to make enchanted weaponry are still extant. You can find useful relics due to their commonality (Sting, Orcrist and Glamdring in the troll hoard, Numenorian blades from the barrows). Also, while few still know how to make them, those techniques have been preserved and are accessible (reforging Narsil into Anduril).
If it was a game rather than a story, I would imagine that the lore would be teachable if you had the grit to travel to Rivendell and persuade the elves to teach you how. Failing that, an exceptional amount of patience to search through the libraries of Minas Tirith to find old records from the Numenorian settlers.
I would say that the rings of power are most definately plot devices. Sauron taught the elves of Hollin how to make them. After seeing their refinements to the process, he encouraged their manufacture and made the One Ring to control the others. At that point, making further rings would only increase his power. While it is possible to make a ring of power, after the elves stop there are no further means to learn how. It seems to be a particularly difficult process; it's implied that Saruman rediscovers the craft, but the ring he makes is basic at best and it took a 1000 years of investigation to figure that much out.
To put this more towards the OP, it is a choice similar to whether or not you think casting
wall of iron is destructive to the local economy. I don't think so, because 9th level magicians are pretty rare and it is unlikely that they will know that particular spell. Furthermore, it would be a pain in the neck to smelt it down unless a special facility was made for just that. I consider that highly unlikely. Because, really, if it was me I would already have all the cash I needed to live comfortably just through the achievement of becoming a 9th level magician. The pursuit of power, the daughter of the Duke's hand in marriage, or whatever my original motivation was would have changed.