Transformers and other electrical equipment containing copper are always sold with the daily copper price in addition to the normal cost. The copper surcharge is therefore always the selling price of the device or equipment plus the daily copper price, according to the upper DEL quotation, on the stock exchange. The stock exchange quotation for German Electrolytic Copper for Conductive Purposes (DEL) is used for this purpose. In addition to the current copper price, procurement costs for transport and storage of 3% and a processing surcharge of 7% are added to the copper surcharge. The copper surcharge always results on the day of invoicing.