There are great articles telling us how do AIs determine which tech to research next and how much would it cost. Well, which one determines a tech's value when you want to exchange it? For example, at sid level, standard map, 8 civs alive, 1st hand nationalism costs 7200 gold to research, and steam power costs the same 7200 gold. But I'm pretty sure that with nationalism you will get steam power and a lot more. On the other hand, AI goes for bronze working in the very beginning almost for sure, but they won't spend much for it in exchange (you can't get wheel or masonry or alphabet by selling them bronze working, can you?). So what's the answer? Thank you!