C HAP TE R 3 Job-costing systems Teaching tips and points to stress Building block concept of costing systems Emphasise that students must master the building block concept of costing systems. This concept is equally applicable to service, merchandising and manufacturing sectors. It is relatively easy to determine accurate costs fora company with only a few services/products. However, many companies have increased the diversity of their product lines over the past 30 years. These different products/services use differential amounts of common resources (e.g. electricity) and this makes it harder to determine accurate costs. This is one reason for companies renewed interest in their costing systems.