What kind of initial patenting costs should we calculate?

With all due respect, I have to take issue with the statement made by Andrew to the effect that it is advisable to permit the inventors to prepare many of the documents themselves - this is usually a recipe for disaster. Inventors are not usually adept at drafting a specification, and certainly not adept at drafting claims. The specification must be in a particular format, and it is important that the specification properly disclose what the invention is, how it works, why it works the way it does, and the like. It is also to be noted that the most important part of the application going into the patent office is the specification, while coming out of the patent office, the most important part of the application is the claims. Why? Because once an application is filed, the specification cannot be changed in any meaningful or fundamental manner. Therefore, the specification needs to be complete, accurate, and thorough. The claims, going into the patent office, or while being examined, can always be changed or amended, but coming out of the patent office, that is, when the application has been allowed and is being processed for grant, issuance, and publication, the claims are the most important because they define your invention. It is best that an experienced patent attorney or agent therefore draft both the specification and claims. Plus, sometimes it requires more time to "revamp" or "revise" an inventor's application than to draft one initially, so I doubt that the time and cost savings is that substantial. Sometimes, an inventor's disclosure may be sufficient to serve as a provisional application, although, again, a provisional application should ideally be as good as a non-provisional application. You also mentioned the fact that you were dealing with a first prototype - a provisional application may therefore be more appropriate for your needs at this time - if you are going to modify or improve the prototype, you can file additional provisional applications with respect to the subsequent improvements, but note that you must file a non-provisional application, preferably including the original prototype and any subsequent improvements or modifications, within one year of the filing date of the first provisional application. If you are also planning to foreign file for foreign patents, you will also need to file a PCT application, or individual country applications, within the one year time frame.