Section 5(2)(a) in The Bombay City (Inami and Special Tenures) Abolition Rules, 1972
(a)in the case of a sale or award in respect of a plot with superstructure, an amount equal to the difference between the amount of the sale price of, or the valuation estimate for awarding compensation for, the plot with the superstructure and the amount of the price of the superstructure only on the date of the sale or the relevant date of valuation referred to in the awarded shall be the sale price of the plot as unbuilt plot;