Is it permissible to purchase goods in installments when there is interest on their original price?

If the buyer purchases an item from its owner and pays the price in installments, and the installment price is higher than its cash price, there is no religious impediment to that. However, if the buyer purchases the item through a bank that does not own the item, but rather pays its price to the seller and collects it from the buyer in installments with interest, then this is pure usury.