The petitioner shall be liable for all reasonable costs incurred in connection with the termination of parental rights, including, but not limited to, costs incurred for the investigation required by this article. However, public agencies and nonprofit organizations are exempt from payment of the costs of the investigation. The liability of a petitioner for costs under this section shall not exceed nine hundred dollars ($900). The court may defer, waive, or reduce the costs when the payment would cause an economic hardship which would be detrimental to the welfare of the child.