The component with the lowest price in the GASKET KIT B schematic is the Washer,plug Drain 14.
Some items from this specific schematic: Gskt.sheet Kit,b (nas), O-ring,5x1.7, O-ring,14.7x3.7, Gasket,l Cover (nas).
On this parts fiche the Washer Sealing 8 is the most specified component.