Some items from this specific schematic: O-ring (1j7), Nut Hexagon 371121580000, Cotter, Valve, Valve, Exhaust.
Of all the components used in this assembly the Valve, Exhaust is the most expensive.
The most reasonably priced component used on the Xt225 Xt225c 1992 (n) Usa California Valve is the O-ring (1j7).