There's a distinct difference between the assembly cost of the individual vehicle and the all-up cost including the original design and testing, so you need to understand exactly what anyone means when they give a "cost".
There's also the argument that MOD doesn't help itself by setting odd standards and requirements that don't necessarily increase the value of the vehicle, although they do affect the cost. Many years ago the MOD decided to do an experiment by putting a frigate out to refit in a commercial shipyard. There was an article in a MOD magazine where they told the story of a windscreen wiper blade. The yard rang the manufacturer of the blades and got a quote for price and delivery. A couple of hours later the manufacturer rang back and said "We're confused - that part number is for a blade used by MOD". The shipyard confirmed that's what it was for, whereupon the manufacturer gave a revised quote with increased price and delivery figures. This was quoted as an example of how suppliers inflated costs when dealing with the MOD. In the next issue of the magazine there was a letter from the wiper blade manufacturer, who said that if the MOD were prepared to have exactly the same blade supplied to commercial standards then they'd hold to the original quote. On the other hand if they wanted all the certification, paperwork, packing and other stuff that MOD specified, then MOD would have to pay for it!
Andy
Andy