GC2 was like this too - the AI valued credits a lot more than it should have in many instances, but not when you were offering credits for their techs.
The AI was pretty stingy in GC2 generally, come to think of it. The only really favorable trades that a player could make were ones where a lot of higher level strategic work was at play, since a lot of their trading seemed to be more anchored in the trade itself at face value. For example, you could convince someone to go to war by offering them some crap techs and credits - or it was worth getting an economic/research alliance early by trading away a lot of your techs and throwing in a bunch of credits - but otherwise you'd never want to trade for techs or credits -- unless it was for a tech that you wanted and couldn't research (because it was not in your tree, such as the massive starbase weapons that the thalan couldn't get, etc).
I expect trading/diplomacy to get better as time goes on, I haven't really figured it out yet as a player, so I don't expect the AI to be there quite yet either.
cheers
