Section 67. Goods manufactured in any of the institutions named in section fifty-one shall, with the approval of the commissioner, be sold by the superintendent of the correctional institution of the commonwealth, the superintendent or keeper of the jails or houses of correction thereof at not less than the wholesale market price prevailing at the time of sale for goods of the same description and quality. The proceeds of such sales shall be paid by the purchasers to the respective institutions from which the goods are delivered.