What is the 80/20 rule regarding software development vs. maintenance costs?

Only ~20% of a system's lifetime cost is initial development; ~80% is maintenance — so fixing things late is where the money goes.

* The inversion — most bugs are born in early analysis/specification, where fixing them is cheap; deferring those same bugs is what drives ~82% of the cost. *

The 80/20 rule in software economics:

• 20% of total costs go to initial Development
• 80% of total costs go to Maintenance

Key insight: "The earlier, the cheaper"

This reinforces why:

• Good requirements engineering saves money
• Security built in early is cheaper than fixing later
• Technical debt compounds over time
• Maintenance includes bug fixes, updates, and security patches