If you want to track costs at the component level, you must check the Post Costs to Components option (EM Equipment, Comp/Attach tab).

Then, when costs are posted to the equipment, they will be posted for the component also. If a component is moved to another piece of equipment, all of the previous costs posted to that component will be carried with it. This allows you to track the costs of the equipment with any component on it, or the cost of the component, regardless of what piece of equipment it was attached to.

Example:

Costs can also be posted to a component when not attached to a primary piece of equipment. Typically, this situation would only occur when the component is in a shop for repairs and has been detached from the equipment to do so. Since components cannot exist independently, you would need to transfer the component to a “dummy” equipment number (the one specified in the Unattached Component Equipment Number field in EM Company Parameters) using the EM Component Transfer program. That way, costs can be posted to the component without affecting the primary piece of equipment.