In addition to the power of eminent domain as provided by law for highways in the primary state highway system, the Commonwealth, acting through the Commissioner of Highways, may purchase any such toll bridge and the approaches thereto with the real estate and tangible personal property necessary for their proper operation, at such time as may be specified in the permit granted for such toll bridge, or at the expiration of any two-year period after such time, all at a price equal to the original cost, to be determined as provided in this section, less depreciation. In order to exercise the right of the Commonwealth to purchase and take over any such toll bridge and approaches and real estate and tangible personal property, the Commonwealth, through the Commissioner of Highways, shall give to the permittee, or its successor in title of record to such toll bridge and other property, not less than two months’ notice of its intention to do so and specify the date on which the conveyance will be required. Title to such toll bridge and approaches and property shall be vested in the Commonwealth free of lien at the time set out in such notice and upon the payment or offer of the purchase price determined in accordance with §§ 33.2-602 through 33.2-610, to such permittee or successor in title of record to such toll bridge and other property, or to the trustee or trustees, or mortgagor or mortgagees in any deed of trust or mortgage on such property, or to the lien creditor or creditors, as their interest may appear of record. The original cost of such toll bridge and approaches and real estate and tangible personal property shall be determined by the Commissioner of Highways. The original cost shall include the actual cost and an additional amount equal to interest at the rate of six percent on the amount actually invested by such permittee, or successor in title of record, in such property, or in hand for investment therein, during the period of construction. “Actual costs” includes the cost of improvements; financing charges; the cost of traffic estimate and of engineering and legal expenses, plans, specifications, and surveys; estimates of cost and of revenue; other expenses necessary or incident to determining the feasibility or practicability of the enterprise; administrative expenses; and such other expenses as may be necessary or incident to the financing of the project and the placing of the project in operation. The Commissioner of Highways shall determine the depreciation and the reasonableness of each item of actual cost.