brehobit
Explorer
I'd argue, as others have, that it's mostly a matching problem. In big cities, there might be a guy who matches buyers with sellers, taking a hefty part for himself. A "fixer" if you will. There might be a few magic items in the city that the fixer knows could be acquired for the right price. And there might be a few people likely to buy a certain type of magic item. But anyone rushing a purchase or sale is going to get hosed. You might litterally be looking at a given item (say a +1 sword) fetching 2000GP (I mean probably more than full plate) but costing 20,000. And weird items might be really valuable. Something that can reliably make ice might be mighty useful in a desert community. A decanter of endless water might be worth 100x a +1 sword in that same place.
Basically, the GM can probably make up nearly any buy/sell price they want and justify it. But if the party lets it be known that they are selling (or buying) and not in a rush, prices would likely get more reasonable. And factiods like "guildmaster Bob has a magic sword and serious money problems he's keeping on the down low" could end up being a wonderful reward from some well-placed person. In the same way, a bit of "starmetal" or whatever might be enough to make a +2 sword with the right tools/magic/smith. And yet another (side?) quest appears.
If things can be easily made, they should probably have a "list price" based on cost to make (labor & materials) and on demand. But things that can't (easily) be made are a different story.
Basically, the GM can probably make up nearly any buy/sell price they want and justify it. But if the party lets it be known that they are selling (or buying) and not in a rush, prices would likely get more reasonable. And factiods like "guildmaster Bob has a magic sword and serious money problems he's keeping on the down low" could end up being a wonderful reward from some well-placed person. In the same way, a bit of "starmetal" or whatever might be enough to make a +2 sword with the right tools/magic/smith. And yet another (side?) quest appears.
If things can be easily made, they should probably have a "list price" based on cost to make (labor & materials) and on demand. But things that can't (easily) be made are a different story.