I love tech trading. There are some issues with the current values though: I can trade late renaissance techs for 3-4k, that seems fair. At the same time if I want to buy these techs from them, they charge 7k+ - a bit too much. Later something happens to civs, and they start offering only 1.5k even for atomic era techs. This is clearly broken, as these techs cost much more bulbs, and I wouldn't sell it for these amounts even to a friend. At this stage of the game its not uncommon to have 1k gold per turn, so... I think even if AI thinks they are "smarter" now and can research everything themselves, this is still a nonsense value.