The most reasonably priced component used on the Mt125a 2015 5d7d Europe 1p5d7-300ek 21 Rear Suspension is the Washer, Plain (7g3).
On this parts fiche the Oil Seal (3c11) is the most specified component.
This Shock Absorber Rr is the most expensive of the items that make up this 21 Rear Suspension assembly.