I've worked successfully with Star Prototype[1] which is a company set up in China by an English gentleman, Gordon Styles - excellent turnaround time on some large CNC aluminium parts. We did a parallel job with a UK based company. Same part, same material. Even with shipping to the UK they took half the time and cost half as much.
I don't know what an electric guitar costs or what its made from (MDF?) but this would be a reasonable starting point. It depends if you just want bits or if you also want assembly and finishing.
My father makes electric guitars as a hobby, though he doesn't CNC them. He makes stencils from acrylic glass (2-3cm thick) and uses them to cut out the body.
If you really want to use CNC for a one-off you should get in contact with your nearest FabLab or Hackerspace. They usually have something around (though hackerspaces often not and if rather small machines)
My advice would be to ask a carpenter to help you out, if you are comfortable with using the tools, or you bring by the (exact) drawings and a block of wood of your choosing. Once again, if you need special kinds of wood, talk to those guys, the should have some nice dry maple and mahagony around.
Two near my house let you use their gear after getting certified (trained). Then you pay per minute.
A third MakerSpace has the gear, but they operate it for you. I was prototyping a laser engraved product. Working thru someone else's hands was expensive and unsatisfying.
"The cost is much higher than a mass production case (likely 50-200+ times more expensive)"
Mass production case has two advantages. Big batch size and insignificant cost of design/product. For the CAD-work I would pick someone I can meet personally and often. After that, if you pick plastic, you have multitude of options how to produce the prototype. However it's "only" hundreds of dollars now. Casting, CNC and 3D printing are all competitive options for crude model.
For refined piece like the example, i'd seriously consider making aluminum permanent mold for a casting run. It's good for production run of few thousand products, while CNC milling aluminum mold is not very expensive. You have to spend bit more time in design phase, because now you have to think how the finished piece exits the mold, etc. But the good thing is that this is identical to the mass production tools you are eventually going to order. The only differences are the hardened tool steel as material and possibly Electric discharge machining replacing CNC.
I wonder what the cost/turnaround time for a one-off prototype would be?
For these work piece sizes and materials, you can do it yourself for ~$3,000 USD one-time hardware cost:
* Sherline 3-Axis 5400 CNC-ready* [1] $1,300 USD
* Stepper Motors + Controller[2] $500
* PC + parallel port $500
* Measuring and holding tools $500
+ Materials
+ CAD/CAM software
+ Several hours/days of time for setup and machining
The cost of these materials is low, so I guess you could make a prototype like this for maybe $50 in material costs? As an added benefit you could machine some or all parts in aluminum, if preferred.
Somewhat related, I really like the NYCNC videos . https://www.youtube.com/user/saunixcomp, showing CNC machining, CAD work - you can learn a lot from those videos!
Can anyone with experience in doing this tell me if it is feasible to get CNCed products made as one offs?
It seems likely that this step is part of a longer and highly involved process resulting in mass production, which wouldn't be appropriate for me.
Can anyone offer experience/tips for getting this kind of CNC work done as a one off. I live in Germany.
Thanks in advance.