What is the ruling on gold shops taking a sum of money under the name of "workmanship" or "craftsmanship" for imported and ready-made gold, knowing that they did not manufacture or shape it?

It is permissible to purchase gold with paper currency, and the seller is allowed to add the manufacturing cost, provided that the exchange takes place in the same sitting, because gold and currency are different categories. As for exchanging old gold for new gold while paying the difference in price for manufacturing, this is not permissible, as it falls under usury. The Prophet, peace and blessings be upon him, forbade preferential treatment in the exchange of gold for gold. The correct method is to sell the old gold first and then use its price to purchase new gold.