What did David pay for his first wife?

200 Philistine foreskins

(Saul had only asked for 100 foreskins, but David was feeling generous.)
David ... slew of the Philistines two hundred men and David brought their foreskins... to the king, that he might be the king's son in law. And Saul gave him Michal his daughter to wife. 1 Samuel 18:27