I suspect that *part* of the issue with Trading is the level of Abstraction that makes 11 of something worth exactly the same amount as 100 of it, making it easy to game the system by trading for 100 of something and then selling it off in nine batches of eleven. But honestly this is the sort of thing that a GM can just plain veto. I would suggest that a GM is well within their rights to insist that if you have 100 units of rare alcohol, then that is one vast quantity, not nine vast quantities.
Otherwise I suspect that the way to curtail this kind of thing is to remember that acquiring gear is no more intrinsically abstract than any other part of the game mechanics. If you *want* to try to sell your Legion Krak Grenades then you need to roleplay out finding somebody who wants Legion Krak Grenades, haggling over a price, and handing them over.
It might also tame things a bit more if Traded items were assumed to be consumed even if the roll is a failure.