Clearly Macca is including R&D costs in his $15,000 budget, which I can see as being reasonable.

However, my estimate puts mold costs at <$5000, and it doesn't matter really if its curved or straight, twisted etc., just means you need to find a 5 axis CNC vs. a 3 axis CNC. How many out there have designed something and then built it? Namely how many have designed and built molds? I have and its not a trivial process. You need an aero engineer that knows what he is doing for the foil design, you need a solidworks or other CAD package guru to model the foil properly, and you need a mold guru to aide the CAD guy in tooling design. Then you need a structures expert to design a layup schedule that won't explode under sailing loads, which are hard to predict making his job difficult. Where you spend the money is important, you can reduce the production costs with good design work but often it is easier and safer with composites to build the piece, load test it and make changes to the layup from there. Of course this all has to be repeated to some extent if the foils are asymmetrical.