I am thinking that a 20 fps camera's lenses would need to have a VERY robust and sophisticated automatic diaphragm OR, since the camera uses no mirror, perhaps the lens will stop down to shooting aperture and stay "closed" as long as the shutter is depressed. Decades ago, Nikon developed the first battery-powered "motorized" camera, way back in the 1950's, and within 10 years made all Nikkor lenses with ball-bearing diaphragm mechanisms, so they could handle the stress of being used on the motor-equipped F-series cameras. But 20 fps? I think that might warrant a different lens diaphragm system than the 35mm-system lenses are using. I really have not checked into this new 1-series camera yet. Might read what's available later today.
As far as a $1,000 70-300 VR lens designed specifically for this new camera; that is expensive, but it might, and I say might, be the result of making a very high-quality lens with superb optics. The higher the initial retail price is on a Nikkor lens, typically the higher the lens's image quality turns out to be. That's long been a "thing" with Nikon's lenses, and especially the zoom lenses. High retail price allows more-complex, better-performing, and better-constructed lenses. I don't know yet, but the new 70-300 VR "might" be a professional-grade lens, made small, and made with slower maximum aperture so as not to make it huge and heavy. 70-300mm has long been the province of "consumer" type lenses, but keep in mind,
Canon currently has a $1,429 70-300mm f/4-5.6-L IS USM lens...
Canon EF 70-300mm f/4-5.6L IS USM Lens 4426B002 B&H Photo Video
This Canon 70-300 has two Ultra Low Dispersion lens elements, and a floating element design (floating element lens design is a Nikon optical invention, dating to the 1960's...) to improve image performance from close range to far. It's a "pro-grade" lens design, even though the majority of 70-300 lenses sold are either beginner-level, or consumer-level.
