The Chilcot report into the Iraq war cost £10,375,000.00. It consists of 12-volumes containing 2.6 million words.
(The inquiry was launched on 30 July 2009, to cover the period of 2001 to the end of July 2009. Over 100 witnesses were called.
The findings of the report were that British military action was not the last resort, that policy on Iraq was made on the basis of flawed intelligence that was never challenged, and that the overall severity of the threat posed by Iraq, particularly the existence of weapons of mass destruction, was grossly overstated, and presented with a certainty that was not justified.)
The whole report can be downloaded here: http://www.iraqinquiry.org.uk/