§ 40. Exchange of unappropriated state lands. The commissioner of general services may, from time to time, exchange a part or all of any parcel or parcels of unappropriated state lands for real property required by or of benefit to the state of New York and in which title is held by the United States of America or a city, incorporated village, town or county when the combined value of such unappropriated state lands and required real property does not exceed five hundred thousand dollars. An appraisal of the value of the real property to be acquired by the state and of the property to be conveyed by the state shall be completed by a qualified professional real estate appraiser. If the value of either property is in excess of one hundred thousand dollars, two appraisals of that property shall be required prior to the exchange. The terms and conditions of such exchange, including any monetary consideration to be paid to equalize the value of such exchange properties, shall be subject to the prior approval of the state comptroller. The attorney general shall approve the title to the lands to be thus acquired by the state.