What is the game mechanic behind a tech trade?

[gavenkoa]

I don't understand why AI refuses to trade some tech and condition when he becomes ready to trade.

I also noticed that initially AI wants more and later is ready for 1:1 exchange.

Some AIs are greedy (I have trading with Kubai Khun). Is it really the case?

As I understand AI may refuse to sell Wonders, Victory, War related techs...

Some parameters are described here: http://modiki.civfanatics.com/index.php?title=Civ4LeaderHeadInfos

 

[gavenkoa]

I tried to read CvGameCoreDLL/CvPlayerAI.cpp function AI_counterPropose and it's pretty complicated to understand ((

 

[AcaMetis]

The more players (human or AI) that know a specific tech, the less that tech is worth in the eyes of the AIs. I don't know exactly how much more/less AIs value a monopoly tech (only one person knows it) over a "Toku tech" (everyone but one person knows it), but it can mean the difference between getting a trade and not getting a trade. I'm pretty sure Lain ran into this issue at one point, where he checked two trades he wanted to do, but the second one no longer worked after he made the first trade because the tech decreased in value. Don't remember what series that was, though.