Found this on the r6 forum and thought it would be cool to share! It's a conversion to convert a yz450 to a road racer. Might be a fun winter project for someone.
It says on there the average cost of a build is around $4200. I'd assume thats with the cost of the frame/motor. It seems like a lot of the cost depends on the accessory items you add. Exhaust/brakes/etc etc. Depends on if you want higher quality or cheap.