Making a Pen with Fewer Parts

A retired engineer from International Harvester once told me a joke. He said if John Deere could make something with 9 parts, then International could make it with 11.  Currently, my pen design requires 6 pieces - two stock items and four custom machined parts. While I cannot do anything about the stock items, the refill cartridge and twist mechanism, I'm almost certain that I could design it with only 3 custom parts, and maybe even 2. Achieving simplicity not only saves money, but for me, is desirable for its own sake. That is so long as it doesn't compromise the functionality of the final product! I doubt the end user really cares about how it was made. He or she only cares about whether it works or not. And the customer's opinion is the only one that matters, because I making this pen for the customer, not for me.