Determine the cost of goods manufactured (COGM) using the LIFO (Last-In-First-Out) costing method, with the following data: beginning work in process inventory of $40,000, direct materials used of $60,000, direct labor of $50,000, manufacturing overhead of $30,000, and ending work in process inventory of $20,000. Elaborate on the LIFO costing method and its suitability for inventory valuation. Provide detailed calculations and insights.