Common rail Diesel Pumps are far far far from cheap, Even for the OEMS!!!!
Modern common rail injectors, pumps, rails etc are all mega cash because they have to cope with 200-2000BAR!!!!! (bear in mind that most petrol engines run at 5Bar tops) and they have to meter out tiny tiny tiny volumes of fuel.
Thats why the derv engined option of a car is more money than the petrol equivalent.