ASAIK diesels are also cleaner than petrol engines - certainly in terms of CO2 emissions.  There is no technical justification for the 5K price differential.  Diesels are only marginally more expensive to produce than petrol engines when produced in large volumes.  It must be the low volumes sold in the US that creates the differential - that plus VW making money where they can.  German manufacturers are not noted for price discounting to gain market share.

notes from no w here