Under Material, make selections for Class and Name if they are not populated. The Class and Name are populated if the material in the part matches a class and name in the machining template.
If you want custom classes and materials to appear in the Costing Task Pane, create a template with material information and information about how the materials will be machined.
The Material cost is the cost in the template for the selected Class and Name combination. You can override Material cost without editing the template. Overrides affect only the part that is open, not the template. If you override Material cost, the text box appears in yellow.