Review of the Blade F16 plans? Well, I am pretty biased as I count Phill as a friend.
To build to the plans there is some stuff you will have to think through, but that is the case with all building projects. I think the plans are good. They would be better if illustrated by a professional, but all you need and then some is in the plans for the ply Blade F16. However, as a first ply/epoxy project, it is a large project. Instead of plunging into a 200+ hour project, how about doing a plywood kayak from
http://www.clcboats.com/ to get to know the tools, materials and processes. Better to cut your theet on a small project than learning the hard way that building was perhaps not what you thought.
Cost.. The answer to this will always be "it depends". It depends on what gear you put on the boat, how you get a rig on it, sails, foils, rudder system, lines, building materials, how you use those materials, tools you need to buy, renting a building to house the project. Manufacturers can often strike deals with Harken, SP and others so they buy all their stuff at a lower cost than you can. If you know where to get good deals and have the right connections, homebuilding can be done cheap. If not, your boat might cost more than a new one from the manufacturer! An estimate for a first go with some reality in it might be the cost of a new boat minus 20%! Buying something used is attractive..
When I did the first boat, I bought a wreck of a Tornado for the gear and the rig. I then went on and spent 8 years sailing tornados instead of the boat I had built. Buying the wreck of a beachcat for the gear can be a money saver, but it can also seriously sidetrack your project. Sailing is even more fun than building..
You still have not shared why you want to build. As I wrote earlier, I definately dont recommend someone to begin building unless they are doing it to enjoy the process of creating something. If the goal is to save money or go sailing on something special, there are some long odds that the project will not be completed. Sorry to say so, but it is much better to get all warnings and think things through before spending money.