A kid is the standard biblical fee for a prostitute. See Genesis 38:17, Episode 19, where Judah paid for sex with his daughter-in-law, Tamar, with a kid.
I thought you hated her. (15:2)
Samson's father-in-law thought Samson divorced his daughter because he hated her - which is what a man does in the Bible when he hates his wife. (Deuteronomy 24:1, Episode 75)
Take her instead. (15:2)
Since Samson's wife was now married to another man, he could never take her back. That would be an abomination to God. (Deuteronomy 24:4, Episode 75)