I get this question a lot, particularly from inventors or startup business owners that have a great idea for a product, but have not yet focused on development of the concept into a product. The short answer to the question is “Somewhere between $3,000 and $3 Million”. A better answer will depend on a number of variables that drive the amount of work required to get to the prototype needed.
The first variable that drives a prototyping project is design. If an acceptable design for the unit has already been produced, prototyping is purely a fabrication exercise. However, most concepts have not been design or engineered to a level that allows production of a prototype. In these cases, the project quickly transitions to a product design / development focus, because this has to happen before prototype development. If the design needs to be developed, it is also important to consider whether the basic science behind the concept also needs to be developed. For example, can the prototype functionality be achieved with a combination of commercially available components, or is true R&D required to develop the critical subsystems?
Another really important cost driver is what the prototype will be used for. If the prototype is purely for a technical feasibility check, a rough look and aesthetic may be perfectly acceptable. If specific technical questions are to be answered by the prototype, it may also be acceptable to omit some of the other features from the unit. However, if the prototype is going to be used as a demonstration piece at a trade show, ergonomics, aesthetic, fit, and finish need to be excellent. If the prototype is to be the first in a succession of rapid iterations (as described in “The Lean Startup” by Eric Ries), it is important to have a plan for what information will come from each iteration.
Development budget is critical in choosing a path to prototype as well. When large companies begin a product development and prototyping project, they define a budget as one of the first steps: startups should be doing this as well. If a budget has not been considered, it is probably too early to be sourcing a prototype. Even if the budget is small, meaningful design and prototype work can often be executed to help determine if further investment is warranted.
The final, and probably most important consideration is the long term goal for the concept. What are you going to do once you have the prototype done? If the intent is to build a business around the concept, what are your pro-forma cost targets and volume expectations? The answer to this question drives material decisions and feature sets in production units: so if the prototype needs to be representative of production units, this needs to be defined early.
Production of one-off units and prototypes is easier now than it has even been. But the work that must happen before and after prototype fabrication still drive the cost, time, and effectiveness of the physical prototype.