Prototyping is essential in my design process, and during the course of projects I use it to evaluate ergonomics, fit, and assembly and such.
I have a dual head FDM printer, and use water soluble PVA for the support material when needed. The PVA increases the cost, but makes a massive difference in the quality of certain parts.
To keep the charges simple, instead of calculating the cost based on printer time, and how much each type of filament costs, I simply charge 20 cents per gram. This includes the filament used in the wipe tower.
The below example is an 85 gram print, so that would be $17.00 at 20 cents per gram.
