The aerodynamics and research that must have done into this the building of these racing yachts is unreal, let alone the cost of the actual construction. Overall, we know know that Larry Ellison, CEO of Oracle and owner of the winning yacht, BOR 90, spent over $400 million dollars on his team's America's Cup campaign- that's twice what they spent in 2007 when there were eliminated in the Louis Vuitton series. The boat itself is rumored to have most more than $50 million, including the backup and spare pieces that were produced and never used. Apparently with pieces of this size, the team had to build backup sails in case any were damaged. The initial budget was said to be somewhere around $10million when planning began in 2009, but that number quickly sky-rocketed. Each sail was said to have cost hundreds of thousands to millions of dollars, and each has a life-span measured in hours.
BMW Oracle made headlines everywhere when they decided to go with a fixed wing- only the second to be used in an America's Cup race. Also taken into consideration was the number of hulls on the boat-- three for this trimaran, as opposed to its competition (Alinghi of Switzerland)'s catamaran with two. According to a variety of articles I've read, the fixed wing was initially designed to be 80% the size of a Boeing 747 wing, but in its final production was over two times the length measuring in at more than 220 feet. The vessel is the size of two basketball courts.
There is so much more that goes into the design of one of these things, I am hardly knowledgeable enough to go on, but this article does explain a little more about the technology they have been developing and are using.
*Sources: CNN.com, Wikipedia, AmericasCup.com, SailingWorld.com