For the purposes of this chapter, facilities shall be maintained by the state for the care, treatment, and maintenance of the psychiatrically disabled, and the patients may be maintained and treated in the facilities or in foster family care, and may receive the services conditioned upon prompt and regular payments for the care, maintenance, and treatment or for the services in amounts as fixed by the director. In the discretion of the director, the rates so fixed may be the reimbursement rates or in excess thereof. A preference shall be given to persons whose estate, or the person or persons legally liable for their support, cannot sufficiently pay for the care and treatment, or for the services in licensed private facilities or from sources outside the department. The director, in the director’s discretion, may accept payments for services at less than the reimbursement rates, but the acceptance of the lesser payments shall not release the patient, the patient’s estate, or relatives, if they have sufficient financial ability, from the obligation to make up the difference between the amount fixed, accepted, or paid and the full reimbursement rates.