The Real Cost of Software Maintenance vs Building

Barry Boehm's research shows maintenance consumes 50 to 80 percent of a system's total lifetime cost. The 60/60 Rule is more specific: maintenance is roughly 60 percent of lifecycle cost, and within that, 60 percent comes from changing requirements. That means the world changed and the software had to change with it.

In a clean system, maintenance splits into enhancements, bug fixes, upgrades, and proactive improvements. In an interdependent system, a significant slice goes to keeping components in sync that shouldn't need to talk to each other. Manual data reconciliation. Emergency patches for coupling-related incidents. Meetings about why the sync broke. That's not maintenance. That's paying the Sync Tax.