In this Act, unless the context otherwise requires,-

(h) Sale price means the amount payable to a dealer as consideration for the sale of any goods, less any sum allowed as cash discount according to the practice normally prevailing in the trade, but inclusive of any sum charged for anything done by the dealer in respect of the goods at the time of or before the delivery thereof other than the cost of freight or delivery or the cost of installation in cases where such cost is separately charged;

Provided that in the case of a transfer of property in goods (whether as goods or in some other form) involved in the execution of a works contract, the sale price of such goods shall be determined in the prescribed manner by making such deduction from the total consideration for the works contract as may be prescribed and such price shall be deemed to be the sale price for the purposes of this clause