1. Thralling would most likely not be done in front of him, unless he paid for that privilege — it's a trade secret, no two sorcerers/sorceresses would want to share how they get their bread, their butter.

2. Go with whatever seems more fun to play out. For big-stake auctions (exclusive events with high-ticket items), he'd need an in.

3. Yes. Absolutely. Bring this list to me, and I'll give you a merchant-side valuation. As a note: some of it will be completely random, independent of the item's worth in its home world. Please also include what the item looks like, what it can do, and how worn in it is, or if there's a 'story' to it (aka this cloak belonged to 42 queens.)