mid to late game techs can cost 5000-10000 espionage points. that seems like a lot but it is possible with scotland yard to get to 250-500 per turn. 4 turns per 1000. 20 turns per medieval tech. it wont be as rapid as the early game, but it is still worthwhile.
meanwhile if you are teching at a good pace and not worring about stealing.. the cost to sabotage health or happiness is dirt cheap throughout the game and can severly cripple a city. when you have enough espionage you can actually view the city the way you see your own. so its easy to figure out if the extra sick or extra unhappy will hurt worse.
also if war is far off you can pillage towns to nothing in a single turn, and wipe out strategic resources. its too bad they have to make the run back to the enemy each time though. I usually have 5+ spies making runs against the target civ.
NaZ
meanwhile if you are teching at a good pace and not worring about stealing.. the cost to sabotage health or happiness is dirt cheap throughout the game and can severly cripple a city. when you have enough espionage you can actually view the city the way you see your own. so its easy to figure out if the extra sick or extra unhappy will hurt worse.
also if war is far off you can pillage towns to nothing in a single turn, and wipe out strategic resources. its too bad they have to make the run back to the enemy each time though. I usually have 5+ spies making runs against the target civ.
NaZ