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;