The Low Carbon Contracts Company (LCCC), which handles all of the CfDs on behalf of the UK government, said the developers had made a "substantial commitment" to the project.
LCCC said Dudgeon had reached the same milestone as Dong Energy's Burbo Bank Extension, which announced it had spent 10% of expected project costs last week.
The two projects were handed final investment decision enabling CfD subsidies in April 2014. The contract guarantees a fixed price for the electricity produced over 15 years.
Statoil and Statkraft have reached the landmark by agreeing a number of supplier contracts for the project, including a turbine order to Siemens for its 6MW turbine.
Dudgeon's onshore construction began in March, as the substation and cables started to be installed. It is due online next year.