Cost is always a factor when it comes to prototyping. You know you need to produce a certain number of prototypes to test your design. Where do you draw the line on quantity? Is ten castings the right number or should you consider ordering fifteen or twenty just to be safe? Sometimes the limitation on quantity is drawn so tight that there aren’t enough parts to go around for proper testing and evaluation.
The concern is spending too much on the prototypes. This is an understandable concern. But if you address the need up front and in all fairness give yourself enough leeway to have the quantities you truly need for thorough performance evaluation then lay your program out and discuss it openly with the prototyper to find the most cost-effective solution.
Even in the prototyping process where the cost of each part is significant enough to make you think twice about quantity, there is room for maneuvering. There are things that can be done in the prototyping process to give you sufficient quantities without breaking the bank.