Charles Ellicott Commentary Leviticus 27:4

"And if it be a female, then thy estimation shall be thirty shekels." — Leviticus 27:4 (ASV)

And if it be a female ... thirty shekels. —As the woman is the weaker vessel, and her labour is of less value, if she vows herself or dedicates by a vow another woman to the sanctuary, she is to pay thirty shekels, or £3 17s. 6d., provided she is within the above-named limits of age. This was the value of a slave (Exodus 21:32), and is the price at which Christ was sold (Matthew 27:9). It is supposed that under this provision Jephthah might have redeemed his daughter whom he unwittingly vowed to the Lord (Judges 11:30). (However, see Leviticus 27:29.)