Easily track total profit and cost of goods by adding a Cost of Good field to simple and variable products. WooCommerce gives you access to great reports on revenue and top-sellers or earners. Now we’ve added Profit Reporting to make these reports even more valuable for your store! You can evaluate not only revenue, but costs and profit all from within your WooCommerce store. Quickly and easily get the information you need to make marketing and sales decisions to optimize your store’s revenue.
Demo: http://www.woothemes.com/products/woocommerce-cost-of-goods/