If he be poorer than thy estimation - Too poor (to pay) thy valuation. Compare Leviticus 27:7, Leviticus 27:11.
Related Commentaries of Leviticus 27:8
Leviticus 27:8
8 But if he be poorer than thy estimation, then he shall present himself before the priest, and the priest shall value him; according to his ability that vowed shall the priest value him.