Once you have an AI's Territory Map the AI treats it's territory map like crap in future negotiations. I can often buy their territory maps centuries later for
1 gold! In case you don't know, strategically getting updated territory maps are great for planning attacks against them, seeing where their current roads lead (Rights of Passage value) & to see how developed they are. I was hoping the AI Germans or some AI Civs would be more secretative, but ALL AI Rulers give this away for pennies... I mean a penny. Sometimes they might charge 5-15 gold, but that is rare. And WORSE it sometimes increases the relationship you have with them! Talk about making a buck go a long way.