If you get the feeling that this is a question you encounter a lot, you are not alone. We get a lot of calls and emails asking us to explain this question. Of course, the answer is dependent on who is asking the question.
People want to know why they should consider it and, more importantly, the benefit. Sometimes they are simply looking for something to carry back to the project or department.
In order to answer the question, we need to appeal to the broader costs calculated over multiple projects.
We define QA as Process Improvement and processes generally apply to multiple projects (or at least can be applied to multiple projects). Hence the need for long term measurements and metrics.
The simplest example is Defect Management. A simple process to ensure all defects are addressed and handled only once by each member of the team would remove a lot of redundancy.
Other examples include Testcase creation; Testing; Summary reporting; Development; and Requirements management. With the advent of AI, this has become much more critical to get right. The chances of going off track at high speed have increased substantially.