I recently did a trade with Hammurabi and asked him to switch to the pacifism I was running in a golden age just because I had more value to use so I may as well make him waste a turn, another if he changes back, and he had a sizeable military and is my next target so I may as well hurt his gold with maintenance. Then I remembered the AI doesn't pay quite as much in unit maintenance, and I don't know that they have to pay the increased cost for pacifism. Did I just give him a benefit with little drawback, or does he pay more maintenance? I can't recall ever seeing the AI use pacifism unless it was a tiny 4 city empire on the verge of extinction. This is at Emperor level if it makes a difference.