7 Trade Contracts, given from quests in Vabbi, can be traded to a Vabbi Trade Official for a Ruby/Sapphire/Diamond, which are necessary for the 5k Vabbi armor. (That's why they are 5k at the Rare Material Vendor. Very high demand.)
Not many people know this. Thus, you can see a scam waiting to happen, similar to the Imperial Commedations in Factions.
I've seen many people offer 300g-500g per Trade Contract in Kodash Bazaar. 7 of these contracts amount to 2100g-3500g. Since the Gems can be sold for atleast 5000 each, that's a 1500g-2900g profit for doing nothing.
Therefore, don't sell your Trade Contracts for anything less than 700g. That way, they will break even if they are trying to scam you.
There are lots of quests in Vabbi for Trade Contracts. Turn them in for Gems for your armor, or sell them for 700g. But don't undercut yourself.