By building the hulls yourself and buying the rest you can save about 20% of the total cost of new F 16 cat. If you are a good builder and lucky you can build two decent hulls. To get a high performance platform you have to go for at least a carbon mast, and even with that you will have hard to get it down to min. weight.
As for the parts you buy, there is no way to get your money back, this is a development class, and what is good today will be old tomorrow.