Using the charts in Kieth Hartley's The Political Economy of Aerospace Industries, the British government paid somewhere between 29,000 and 6,000 pounds per aircraft in 1946, depending on how you calculate the amortization of the development, and because per-unit costs go down substantially for larger production runs. If you use a weighted average to account for cost changes over the course of the production run, an "average Vampire" cost somewhere in the vicinity of 12,000 British pounds in say 1951-ish. There's a couple of differences in one cam calculate the past value of an amount of money, but depending on the method you use, £12,000 in 1951 was roughly equavalent in buying power to somewhere £1.2 million and £1.9 million pounds in 2014-datum BGP.