It's not the AI making peace with us that's the problem, it's them making peace with each other. I can usually get a peace settlement out of the AI for free, if not then a couple thousand if i can afford it. Problem is, they break the ceasefire immediately by destroying a farm or a town with a single unit of militia, which gives me horrible flashbacks to the AI stupidity of Rome, which we were told had been improved, and which clearly has not.