A basic RED One kit to simply get some 4k (or lower res) cine-style images should be around $22k USD: camera, used Nikkor prime, Nikon mount/adaptor, battery, RED Drive or RED Flash, inexpensive follow focus, inexpensive matte box. This assumes you'll shoot hand held, on an adaptable shoulder brace you already own, or on a tripod you already own. This kit should weigh in the neighborhood of 15 pounds, so a heavy duty (as in expensive) tripod is not necessary. Again, this is for absolutely basic image making with RED One.
The cost of a RED One kit can go upwards from there, depending on what genres of production you do, what you can afford, and what you feel you need to own rather than rent on a per-project basis. If you understand the difference between your wants and needs as a businessperson, you stand a reasonable chance of succeeding in any business - including the motion media business.
Those with a RED One camera body, with the stock PL mount, battery (suggest at least 2), and drives (2), have the ability to bid contract or business media projects, and simply build into the bid/proposal the cost of renting the other lenses and accessories needed for the project, I.E., let the client pay for the rental fees by rolling them through to them in the bid/proposal. Generate the revenue from some of these projects, then use that profit to buy what you'll use regularly. Resist the impulse to have to own everything you use.
To me, some lenses are almost a "no brainer". The RED 18-85mm zoom should be high quality, is affordable compared to other S35mm cine zooms, can be quickly paid for by it's frequency of use, and is usable across a wide range of resolutions, formats, and genres. It's an all-around utility lens. If you can only afford one S35mm lens, it should be a versatile one, so this may be the lens for you. Then rent the other lenses you need (primes, etc.) on a per-project basis until you can afford to buy the primes that you need to own, as justified by regular use of them.
The same rental concept applies to other kit items (tripod, audio, lighting, etc). For example, if you can't afford a top of the line tripod, rent one on a per project basis until you've generated enough capital to buy one. Again, on a permanent basis, buy what you'll use regularly, and then rent the rest on a per project basis.
The RED 300mm prime was a no-brainer for me to buy because some of the genres I regularly shoot require long focal length lenses: sports, nature, etc., I.E., I can justify the outlay for it because of frequency of use. It will pay for itself quickly.
If RED announces some affordable S35mm prime lenses, that could be a cost-effective way to add cine primes into your kit.
Depending on the genres and style you work in, the RED Rail and RED Cage may make good sense to include in your kit.
The RED LCD will be useful for a lot of styles/genres of shooting, but the RED EVF will be necessary for many styles/genres.
Depending on the genres, and thus budgets, of what you shoot, 35mm still lenses can be a viable way to get some affordable, and decent quality 4k images. Cine lenses produce great images – but they are expensive. If you can’t afford cine lenses, use 35mm still lenses until you generate the capital to buy the cine lenses you’ll regularly use. Again, then just rent the infrequently used cine lenses.
Those who are budget challenged, and can only afford the basic RED One image making kit, should seriously think about swallowing their professional pride and seeking contract or freelance work in any logical genre of production to generate the capital to buy the additional pieces of your "dream kit". RED One is versatile and scalable by nature, and thus can be used in many genres and sub-genres of production. If you take a closed-minded approach to the genres of work you'll bid/accept, then be prepared for it to take longer to generate the capital to buy your additional RED One kit items. I think you know exactly what I'm talking about: your goal is to be the next great cinematographer or DP, but you won't "lower yourself" to bidding/accepting low-end cine-style or EFP style work because its beneath your dignity to do so. RED One will be capable of generating revenue in a long list of genres and sub-genres of production. Broaden yourself professionally, and in the process fiscally, by spreading your skill sets to match the capability of RED One. If I have a gap in my production schedule I never turn down work of any kind unless it's subject matter is objectionable to me. Though I regularly do huge projects, I rarely turn down medium or small-sized projects if I have the time and the subject matter is agreeable to me. That attitude will help the budget-challenged pay for a bigger kit - and help the "already arrived" people broaden themselves professionally, and fiscally in the process.
This forum is very cine-centric, so it is regularly assumed and stated that a follow focus and a matte box are absolutely essential pieces of a RED One kit. The necessity of using those is determined by the genre or genres of production RED One users work in. For example, someone using RED One for a 1080p RGB production for HDTV, using a 2/3" B4 mount and HD ENG zoom lens, does not need a matte box or follow focus in their kit for those EFP style projects. The 12-volt auxiliary power can power the servomotors of the HD ENG zoom, thus zooming is via the zoom rocker switch on the lens. Focus is racked by hand on the lens barrel, thus no need for a follow focus. Shooters routinely use screw-on filters on HD ENG lenses, so a matte box is not needed. RED One won't have in-camera filters (ND), so screw-ons will be the way to go with HD ENG zoom lenses.
RED One is a digital cinema camera first, however its not just a cine-style camera, but rather a cine-style or EFP style camera system, depending on how you want to accessorize it, lens it, and what resolution you pick for each individual project.
No matter what genres or styles you shoot, the smart mantra is the same:
Buy what you'll regularly use, and rent all the rest on a per-project basis
Hope this input helps some of you as you approach creating and expanding your RED One kits...