For the purposes of this chapter, the rent deemed payable on account of time-share occupancy shall be the rental value of the unit or room(s) which accommodated such occupancy, which rental value shall be computed by determining the pro rata share of the total purchase price of the time-share right or entitlement (whether or not involving an estate or any ownership in real property) which share is allocable to the period of transient occupancy currently involved, and adding thereto the total applicable operating costs including, but not limited to, the applicable real and personal property taxes, plus the total amount of any and all fees, assessments, charges and expenses (not including the previously referred to taxes) charged by the operator as attributable to the time-share occupancy of the transient by whatever name such fees, assessments, charges or expenses may be denominated, whether occupying fee, management fee or like name or otherwise. In making the computation referred to above of the pro rata share of the total purchase price, in any case wherein the time-share right or entitlement is in perpetuity or for life or otherwise not for a definite or ascertainable term, such pro ration shall be made upon an assumed term of thirty years.