Anyone, anywhere, who has ever had any construction work done by a professional builder knows that you must take whatever is quoted to you at the beginning of the job and double it to get anything close to the real cost of the work.
If you live in London, you can safely treble that sum.
And if you, the client, are a public sector body and need a job finished by a specific deadline, you might as well just print out a blank cheque and hand it over.
So, given how depressingly predictable this story is (is Wembley Stadium even open yet??), why is anyone in the government even pretending to be surprised?
"Culture Secretary Tessa Jowell is being grilled by MPs about the London Olympics, after organisers said costs could rise £1.5bn to £5bn. Ms Jowell is being questioned by the Commons culture, media and sport committee about an unexpected VAT bill for building costs.
The Tories said the budget had gone "disastrously wrong". But Chancellor Gordon Brown said the government was "committed" to making the Games work."