I can never get the AI to trade relics or artifacts. I seem to recall I got a trade in my first couple of games, but now they all ask for ridiculous amounts of GPT as well. Last game with my BFF Hojo, he wouldn't trade. Art, Writings or artifacts. We both hated Vicky, were the sole survivors on our respective continents. I was going for a Science win and even launched a couple missions. I was wanting to practice theming so I was trying to work out trades. I even threw in an extra luxury, but he expected too much cash. So I sent spies and stole them.