Lanefan
Victoria Rules
And who are these shady characters? Why, they're just other adventuring parties trying to unload the magic gear they don't want or need.In the aforementioned city I had the mage meet a rather shady character who deals in arcane items. Now myself, and most of the players are used to a 3E magic item world wherein you sold your sack full of stuff for half price and then bought whatever you could afford out of the DMG. Not so this time around.
This shady character has only a few items, most of which are uncommon to rare, but he's also got a couple of very nice pieces for sale, but they are VERY expensive. Plus, he's only buying items at about 1/5 what he'd be willing to sell the same thing for. So, for example, he had a +1 longsword he'd sell for 5000, but he only offered 1000gp to the dwarf that wanted to sell his own +1 sword. I'm also factoring in relative usefulness of items to their value. I'm kind of making it up as I go, but suffice to say, really juicy magic is very expensive.

How would you handle barter? Say for example said shady character had a +1 axe and the party's Dwarf had a +1 sword but would prefer an axe just because; if the Dwarf offered a straight-up swap what would happen?
Also, what happens if-when the PCs want to trade or sell magic items to each other? You had an example of a Dwarf trying to save up for a belt of dwarvenkind; could he sell his +1 sword to a fellow party member for the full 5000 in order to raise some of that cash? (in other words, buy it from me instead of from that shady character - at least you know you can trust the vendor!)
The rarity of the vendors doesn't matter. The key thing is that the items available for sale be either completely random, or random but logical by which I mean they be the sort of things other adventurers would probably be trying to pawn off.My plan is to make these shady characters very rare in the first place, with random wares
Danger, Will Robinson! Danger!There will be no set prices. Every shady character decides what his items cost and what his market can bare
Be very careful, once the PCs have met one or two or five of these shady characters, that your game doesn't devolve into buy low-sell high economics as they play the market. (it's for this reason that I rather artificially made the price for any given item almost always be the same no matter what)
Also, if you do vary the sell prices it's only logical that their buy prices will vary too: "+1 longsword? Hell, the streets are crawlin' with 'em - last summer I'd have given 1000 for one, but now? 500, tops. But hey, lots of demand for magic maces - I'll drop 1200 if you got a plus-one you wanna part with." But this is where you can end up DMing economics instead of monster-bashing and princess-rescuing - be warned.
What do your PCs do now with any surplus magic items they end up with? If they're able to somehow convert 'em into cash that immediately means somebody's buying them; and if there's any other adventurers in your world beyond the PCs they'll be hitting the same problem - they'll have stuff they want to sell or trade - and boom, there's yer magic market.Has anyone else done something like this? I know that magic sales is deeply frowned upon in the 5E community, but I have to believe that I'm not the only one. I'm curious what others experiences were.
Lanefan