You need to eliminate any fx issues and adjust for PPP to make a truer comparison.
Astonishing train of thought !
Those currency and public private partnership issues would of course amount to a swing of a further £20+ Billion !
Oh and those "Shrewd Turks" are not just getting a mile of tarmac with some add-ons but a fully integrated, brand new airport, built from ground zero, 3 runways plus new terminal capable of 90M !
PPP is 'Purchasing Power Parity' - in otherwords 1 Euro in Turkey has more purchasing power in Turkey than it does in the UK, but like for like, it takes you longer to earn 1 Euro. So, a 10.2bn construction cost in Turkey
not the equivalent of a 10.2bn cost in the UK.
Nothing at all to do with Public Private Partnerships.