Love charging up on the horse on those!
Really?
They should have a floating market value depending on how many are available, your local status (Did you know you can recruit from enemy villages? WTH?) and the wartime status.
Just take a hostle action against a village of the faction you want to go to war with.
Go to the tavern, talk to them. They are slavers they are not ransoming anyone but Lords.
I find his lack of faith disturbing.