I dont think he is planning on building the car himself. He wants to hire a builder, so doesnnt that add to the price? The "builder" has to figure in his cost plus profit like Msaby mentioned.
I have built a LP640 replica, start to finish. I did all the work myself, except for upholstering the seats and dash (darn stitching!), and spent around 52K to date on the build. I didnt charge myself labor, and my build was much easier and less entailed than an AD body.
I think if one of us was to build one of these for ourself, we would spend $60-70k. Remember, the G28 based kits were designed to use cheaper donor parts to keep costs down, which is not the case with the AD kits.
There are countless other issues that need to be addressed when building this calliber of a kit, extra costs that dont apply to G28's.
I spent $35 for my window regulators, but as Onewickedsvt mentioned the OEM ones cost $1200, and are needed for AD kits.