at my work we only charge $18 each (retail)
plus if r&r was 1 hour ($66) for a 4cyl u would only be looking at $138. i think $400 is a ripoff even if u have a v12
the injectors are cleaned in an ultrasonic bath,then backflushed then tested for leaks,flow and spray pattern. all seals, filter baskets and pintle caps are replaced.