I don't understand... He buy Goblin Blood before going in the Dungeon, but didn't he kill (at last) one goblin saying "You where hidden in the same place as before"? If he know he will have Goblins to kill, why buy the blood? (I know, some readers will wrote me "He wasn't sure so he buy it before, but I want to complain )
@Tesla I believe he bought the vials to fill with the goblin blood from the dungeon. Thats why they though it was strange as no materials from the dungeon would be profitable (so there shouldnt be any monster's blood worth using them on).