I've found that the AI sometimes accepts cease fires that are very much not in their favour, but only when you've thoroughly whooped their ass. For example, I took all of spains american holdings, and after that they accepted a cease fire for all their tech and a hefty payment (and new mexico which I didn't bother to take by force). Likewise with France after i took french guyana and louisiana, then threatened Paris with a full stack on the bridge north of it.

BUT, I was drawn into a war with Prussia, didn't share a landborder (as UP) but I was allied with Hannover so I marched through Hannover and took Brandenburg from Prussia. I offer Prussia ceasefire for giving them Brandenburg back. I tried to get a nice payment back for the territory but they refused the deal however little I demanded of them in return. They even refused me giving them back the territory for nothing, even excluding the ceasefire. That's pretty appaling. Even when I took west prussia and they were down to one territory they would not accept a truce under any circumstances I could produce. So I sold west prussia to Hannover for 50000 instead. Of course, they countered my offer of 50000 with 57340.

Silly.