A Mutual Agreement

"Salutations wise leader!

We believe a Research Agreement would be mutually beneficial for our civilizations. We've been good friends for over two-thousand years now so we should each (mutually) put in the lump sum of 350 gold. That's only fair! Of course, it was our idea so you should probably put another lump sum of 200 gold on top of that. We'll call it a finders fee. Then of course, there's interest so we'll take 5 gold a turn for the next 30 turns; that only makes sense. You're also about an era ahead of us in technological advancements already so naturally you should give us all of your oil reserves, and your aluminium, and of course all of your coal... and give us a horse. That all sounds about fair, right?

Wait... what are you saying? You want to adjust the deal?

How dare you! That is unacceptable. I'll think twice before giving out a generous handout like that to you again. This conversation is over."

"And, by the way, I'm the one that's playing with large advantages here! Be coherent, dude!" (assuming of course you're at sufficiently high difficulty settings, )

I agree with you that the AI could be a little more unpredictable and friendlier (more "human") with deals, but I keep having the feeling that they only play the harsh way when you're winning the game. I'm playing a culture game that I'm fairly screwed and all the AIs are playing nice with me...