Certification cost is rarely a single line item. For most manufacturers, the real cost is a combination of consulting time, internal team involvement, documentation development, training, internal auditing, and registrar fees.
The strongest way to control cost is to avoid overbuilding the system. Lean documentation, focused implementation, and strong current-state discipline usually reduce both consulting time and internal disruption.
Companies that start with a gap assessment generally make better decisions because they understand where the real work is instead of guessing.