Notwithstanding any limitation contained in this chapter or any provision therein to the contrary, the commissioner of public institutions is authorized to establish and charge the inmate or patient reasonable fees for the maintenance of each person admitted to a hospital, home or sanitarium under his jurisdiction and control: Provided, That the commissioner of public institutions may, whenever it is deemed just and expedient to do so, exonerate any such person chargeable with such maintenance from the payment thereof, in whole or in part, if the commissioner finds that such person is unable to pay or that payment would work an undue hardship upon him