Leviticus 27:8

And if someone is too poor to pay the valuation , then he shall be made to stand before the priest , and the priest shall value him; the priest shall value him according to what the vower can afford .

If anyone making the vow is too poor to pay the specified amount, the person being dedicated is to be presented to the priest, who will set the value according to what the one making the vow can afford.

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.