In this Act, unless the context otherwise requires,-

(ad). "sale price" means the amount of valuable consideration received or receivable by a dealer 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 delivery thereof, excise duty, special excise duty or any other duty or taxes except the tax imposed under this Act;

Provided that in case of 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 deductions 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 purpose of this clause.