The London Array owned by DONG Energy EON and the UAE MasdaOffshore wind farms aim to increase efficiencies and reduce costs as they grow in size.  Economy of scale is rapidly growing due to partnerships between business and countries who have a long history of developing offshore wind farms.

http://m.spectrum.ieee.org/energywise/green-tech/wind/worlds-biggest-offshore-wind-farm-switched-on-in-britain