The component with the lowest price in the OIL PUMP schematic is the Bolt,hex, 5x20.
Some items from this specific schematic: Screw,pan 4x12, Pin,spg. 4x8, Screw,pan,4x12, O Ring 6x3.
The Oil Pump assembly is constructed from several parts from which the Oil Pump Assy. is the most expensive.