The AIs constantly give each other both economic and research treaties for nearly nothing, but whenever I want an economic treaty from them, even with huge diplomacy and a terrifying military, I literally have to offer them nearly a dozen of my planets, 10k+ BC, and a fistful of battleships, and the economic bonus I get is fairly negligible.
I don't mind economic treaties being hard to acquire, as it's a money-for-nothing everyone-wins deal, but why do the AIs always BEG other AIs to form treaties with them? Even when I have an extremely powerful economy, the best in the game, a 1:1 economic treaty deal that would do nothing but benefit my treaty partner is refused flatly for no apparent reason. They are toppling into bankruptcy, but they refuse.
To be honest I think one thing that would help this game a lot would to simply have AIs focus more on themselves and not others. I've been playing as Terrans and I've noticed that the AIs are always FRANTICALLY declaring war, peace, war, peace, and war again over and over, and then come crying to me as I'm usually friendly with everyone at this point. They trade away things to each other without rhyme or reason, and form obscure treaties that shouldn't exist (Torians in treaties with the Korath clan? Uhh huh).
The depth of 'insider trading' of the AI's relations just gets a little too much sometimes.