What is expensive?
Now I don't know any details on Nimrod, nor do I seek to defend BAES and its commercial behaviour, however, when bemoaning cost escalations and what seem like massive costs, it must be bourne in mind that complex engineering is always expensive - this is a harsh reality & not something you can pretend can be avoided.
As a quick comparison, which is a bit rough around the edges, compare some of the costs bourne by Microsoft. It spends $7Bn / £3.5Bn per year on R&D. For the sake of argument, lets guess that say 1/3 of that is spent on their core product - PC operating systems. MS VISTA took 5 years to develop, from 2001 to 2006, hence taking approximately £6Bn to development. It contains 50 million lines of code.
Compare now to Nimrod MRA4, which apparently has 6 millions lines of code - OK not as much as VISTA, but then again each copy of the software comes with quite a large free aeroplane. Total cost is £3.6Bn. Now this is alot of money, but I think this perception is particularly exaggerated when it equates to £300m per copy, when you only buy 12.
By comparison, if Microsoft only sold 12 copies of VISTA, each one would cost £500m - with no aeroplane.