Software maintenance starts from day one of a project and inspected software is less expensive to alter, fix and maintain

Software maintenance starts from day one of a project and inspected software is less expensive to alter, fix and maintain.

Research has yielded these findings:

Fixing defects early cuts costs in half. Correcting defects earlier rather than later in a project can cut overall development costs by factors of two or more.
Catching defects during testing is 10 times more expensive. Construction errors detected during system testing cost 10 times more to fix than in the construction phase and 10-25 times more to fix when detected post-release.
Debugging represents half of development costs. Debugging and associated rework takes about 50% of the time spent in a typical software development cycle.
90% of development work occurs after initial release. As much as 90% of development effort on a typical software system comes after its initial release, with two-thirds being typical.
25% of requirements change during development. The average project experiences about a 25 percent change in requirements during development.
70% of rework caused by changing requirements. 70 to 85 percent of rework on a typical project is caused by changes in requirements during development.