Gotcha, that explains the massive costs when asking for an AI to do so then.
However, I see the AIs flinging this back and forth quite often - over the course of three turns I saw seven Ceased Relations messages, five of which were directed at Shaka of the Zulu, then three more over the next few turns. Given how much I have to pay for a cease relations even towards a leader the AI I'm asking hates, I'm surprised the other AI's aren't bankrupt by now, unless they're getting free passes on this.
Though, Ceasar is somehow the tech leader in the game with only four cities (Three of which are tundra-locked) and he's been asked to Cease Relations the most, so I figure people must have been giving him a ton of techs in the deal. There's no way he could out-tech Mansa Musa, Alfonso, or Justinian who all have very nice land and three times the number of cities on his own.