Mark, the price hike was purely due to the relatively low volume, and the different mechanical components. Engine, whilst designated M100 had absolutely nothing in common with the 6.3 unit. Whilst some items could be shared with the 450, such as the fuel system (K-Jet, Injectors, Fuel Pump and Auxiliaries, the cost of engine components themselves, the variation in size of the gearbox casing and some of the internals, plus a diff ratio exclusive to the 6.9, just pushed up the price.
The main difference, of course, can be traced to the suspension system. No need for me to enumerate on the various changes, but obviously they were substantial enough to really push up the price. I guess that's where it stands. The volume of production was slow by major manufacturing numbers, and every engine was bench tested, I think, for many hours. Plus we had a Ch. 116 flagship, and it was a privilege that one would have to indulge in. Those are my reasons. Regards Styuria