Apple has been working with British firm Foster + Partners to try to cut $1 billion from the budget before proceeding – an undertaking that has caused expensive delays, according to a report by Bloomberg citing five people close to the project.
Costs have also been pushed up by the unique features specified by Apple's late co-founder Steve Jobs, who insisted on having no visible seams or gaps in the construction, using polished terrazzo rather than cement flooring and harvesting all interior wood from a certain species of maple.
The building's curved glass exterior will reportedly require six square kilometres of glass to be bent and shipped over from Germany by manufacturer Seele GmbH, which has doubled the capacity of its plant to supply the Apple project.
Originally scheduled for completion in 2015, the move-in date for the campus has now been pushed back to 2016.
Many of Apple's rivals are also building new headquarters in California, with Facebook last week given the go-ahead for its Frank Gehry-designed open-plan office and Google revealing plans for a 100,000-square-metre campus in San Francisco Bay.
Last week it was reported that the highly anticipated Apple television, set to launch later this year, will be operated with a digital "iRing" worn on the finger – see all news about Apple.
Images from Cupertino City Council.