The component with the lowest price in the CYLINDER HEAD schematic is the Screw,cross 5x28.
Parts such as the Cylinder Head: Spark Plug(ngk), Screw,cross 5x28, Gasket,cylinder H (nas), Nut,cap,6mm are included in the Nx650 Dominator 1989 (k) England / Mkh Cylinder Head parts fiche.
Of all the components used in this assembly the Head,cylinder is the most expensive.