The most reasonably priced component used on the Dr-z125 2003 (k3) Usa (e03) Drz125 Dr Z125 Seat (model K3/k4) is the Cushion.
This schematic depicts all components used in the Dr-z125 2003 (k3) Usa (e03) Drz125 Dr Z125 Seat (model K3/k4) partslist.
The Seat (model K3/k4) assembly is constructed from several parts from which the Seat Assy is the most expensive.