There are a multitude of variables affecting gearbox costs which make it difficult to determine how expensive a unit must be for a given application. The trade-off between design conservatism and cost is always present, the goal being to achieve satisfactory performance at minimum price. The cost of a gearbox can be divided into three elements: material costs, manufacturing costs and purchased items such as bearings, seals, lubrication components, and so on. The gearbox configuration, parallel shaft with an offset between input and output, or planetary with concentric shafts, will also affect the system design and influence costs. The cost question then focuses on what materials to use and what degree of quality to require in the gearbox components. When manufacturing gearbox components, the time to set up the equipment far exceeds the time required to machine the parts. Therefore, it is far more expensive to perform a machining operation on one part than on many parts.