shrewd trade edge bug

Ok, I've suspected something, but this *has* to be a bug. I have the shrewd trader edge. I bartered a dragonorb, worth 25 gold, for an item that cost 1750 copper. I only received three of them. I tried to barter the dragonorb for at item worth 10000 copper, but Urasio said the deal wasn't worthwhile. I don't barter a lot, but I'm thinking something off with the math as items get higher priced. Log below: <876hp 100% 50% 24350tnl 2 AM wilderness> iYou are carrying: (Glowing) the diamond dagger named 'Light of Redemption' a single sheet of aged parchment a stone baton (Glowing) (Humming) a razor-thin dagger 'Storm Shear' (Glowing) a dagger named 'frostbite' a linen needlework the girdle of endless space the Cuendillar Dagger of the Empress (Humming) a long titanium spear <876hp 100% 50% 24350tnl 2 AM wilderness> get dragonorb girdleYou get the jade dragonorb from the girdle of endless space. <876hp 100% 56% 24350tnl 3 AM wilderness> hideThese shadows are too uncivilized for you to hide in. <876hp 100% 56% 24350tnl 3 AM wilderness> A witch closes her eyes with a look of concentration for a moment. A witch is surrounded by a resistance to acid attacks. <876hp 100% 56% 24350tnl 3 AM wilderness> barter dragonorb for spores womanA witch nods at you with approval. You hand the jade dragonorb to a witch. Three times, a witch hands the spores of a sundew to you. <876hp 100% 79% 24350tnl 7 AM wilderness> list all woman[Lv Price] Item (Type) [40 31250] the jade dragonorb (talisman) [30 3125] a pink orb (talisman) [42 1750] the spores of a sundew (trap ingredient) [33 225] a small vial of fairy dust (trap ingredient) [10 6] a violet potion (potion) [10 250] a sprig of dried herbs (pill)