My rationale is that this figure covers purely the material/chip costs of the kit where the rest is for my labour/life time assistance with installation and usability issues, a fair and honest argument I believe. It also obviously reduces customs fee impact worldwide.
I'm also trying to automate my production so I can start to lower prices. I expect Chinese copies to come out that I know I can compete with quality wise but will have to do better with prices in the not too distant future. In a full work day only 10-15 adapters can be produced right now. With a second machine coming and with automatic tool change capability (exactly this one
http://www.youtube.com/watch?v=9X5AS...ure=plpp_video) this should more than double without requiring me or my father-in-law to be 100% at the machine during production.
As for the term "universal" FDn mount. You are right, it is not universal, every lens has its own unique issues with aperture lever connection and many will have 5D mirror interference issues. When I do start to sell kits, they will all still be very lens specific and will clearly list issues and incompatibilities with certain camera bodies.
As for screws, I usually provide new ones. This way people can drill the heads off and then put vise grips on the studs. Also heating up the screw with a soldering iron with some solder on it has helped releasing some really tight fit screws without breaking them for me.
I expect a kit for the 24-35 as well but I'll start with the 20-35 first.