Yes, because they wouldn't have to pay for the support structure, tooling, bays, plumbers etc over the predicted life of the aircraft, but the replacement ballast design would have cost more than fitting the gun, so it was fitted but inactive, then later on someone figured out having a working gun might actually be of some use.
Which makes you wonder if pulling out the systems designed for this plastic pig at the offset, oxygen systems, bang seats etc, will make the need for a redesign to accommodate the changes and possibly ballasting to retain the C of G necessary. Indeed, will the savings be offset or lost by the changes involved.