VW Services are a *******

Can someone please explain to me why they would charge R3,280.00 for a 120,000km service to a VW Caddy 1.6 Petrol, yet R1,800.00 for the same service for a Caravelle 2.5 TDi?? Whenever we take our Caddy for a service, it is damn expensive, not to mention \everything else"they charge us to fix because this caddy has an irritating jerk/misfire"