The cost of noble metal catalysts is high, and due to the scarcity of noble metals, the overall cost of fuel cells is even higher (Table ). Indeed, the natural scarcity of noble metals (NMs) largely determines their high cost. Common non-noble metal catalysts, such as iron, cobalt, and nickel, are usually more abundant and less expensive than noble metals. Table shows a clear difference between the cost of noble metals and non-noble metals. For example, the price of iron per gram is $0.0001274, and the price of platinum is $28.99, which is approximately 2.273 10 7 % of iron. Though the price of non-noble metal catalysts varies, it is × still significantly cheaper than noble metal catalysts. Although these prices are subject to change, they can provide a good idea of the difference in price between noble metal catalysts and non-noble metal catalysts, which helps explain why certain industries decide to use non-noble metal catalysts as their source of a catalyst even though they lack the same level of efficiency.