Do exhibit items from the Curse of the Dark Pharaoh expansion count as tradable items?
Yes, Exhibit items can be traded like other items.
From the Curse of the Dark Pharaoh rules:
The Exhibit Item cards represent the ancient Egyptian artifacts brought to Arkham as part of the "Legacy of the Pharaohs" museum exhibit. They are similar to Unique Items, but have no monetary value and can only be gained through Arkham, Other World, and Exhibit encounters.
This states that they function the same as Unique Items, but does not disclude them being traded.
Also from the Complete Arkham Horror FAQ (page 4/5):
Q: Exactly where, when, and what can investigators trade?
A: They may trade Common Items, Unique Items, Spells, the Patrol Wagon, the Deputy’s Revolver, Exhibit Items [CotDP], Rail Passes [DH], and Money.