Albert Barnes Commentary Leviticus 27:4-7

"And if it be a female, then thy estimation shall be thirty shekels. And if it be from five years old even unto twenty years old, then thy estimation shall be of the male twenty shekels, and for the female ten shekels. And if it be from a month old even unto five years old, then thy estimation shall be of the male five shekels of silver, and for the female thy estimation shall be three shekels of silver. And if it be from sixty years old and upward; if it be a male, then thy estimation shall be fifteen shekels, and for the female ten shekels." — Leviticus 27:4-7 (ASV)

The relative values of the persons appear to be regulated according to an estimate of the probable value of their future work:

As regards the shekel of the sanctuary, see Exodus 38:24 note.