I'm running a campaign for a group of friends who - while not new to roleplaying - are new to the idea of a generic resource points system. For context only (still system-agnostic advice), I'm talking about Burning Wheel, specifically during character creation.
Generally, I interpret the RPs system to list all the items your character always has with them - called 'props' in some systems. Things like a special obsidian dagger, or some such. Or a house.
However, as I'm finding out this opens the system to abuse. Imagine the following conversation:
Player: Can I have this really expensive shield?
Me: Well, yes, but it's really expensive. You sure?
Player: Oh, well, my character is a blacksmith - they probably found the metal in a scrap metal bin.
Me: Well, that should logically reduce the cost, and it's fully reasonable... but honestly, that just makes it stupidly cheap. NO: GM FIAT
However, this discourages players - they become frustrated with the fact that their resource pool no longer makes sense, especially in a game like Burning Wheel, where the system is entirely logic. In short, how do I encourage players to come up with creative stories for how they got their possessions, while not totally breaking the resources system, and not discouraging them from getting expensive stuff?
Should I be forcing this at all? Or should I accept the logical decrement in cost and leave it at that? Additionally, what do I do when players are very persistent in finding ways around the RP system?