ODA chairman John Armitt told the London Assembly last Wednesday that the final cost of the 80,000-seat athletics venue would be £496M.
He defended the apparent rise from the 2004 bid cost of £280M.
"This figure is absolutely in line with the announcement by the secretary of state [on the total £9.5bn Olympic budget] and has not gone up," he said.
"To suggest that costs have doubled from the bid book presents a grossly misleading picture for the public. This figure is a 2012 outturn cost."
The cost, said Armitt, includes VAT, legacy conversion, some site earthworks and inflation at a rate of 6% – broadly in line with cost consultants' forecasts of construction inflation in the capital until 2011.
As revealed by NCE the stadium will be a bowl-like structure dug into a sloping bank housing 25,000 permanent seats. Above these will sit an additional 55,000 temporary seats (NCE 20 September).
Full designs of the venue will be revealed in two weeks by the ODA and Team McAlpine, the venue's design and build consortium of Sir Robert McAlpine, Buro Happold and HOK Sport.