It's hard to quantify that time. MBWA (Management By Walking Around) can be very beneficial, but difficult to describe. Some activities (like Risk Assessment/Reassessment, Budget work, Change Control) can be easily quantified because there is a result. If there's no deliverable, it can be a challenge, but those activities are necessary. If someone questions the value, ask them if they think the project would succeed if that activity were omitted. And you can ask them if they have any ideas regarding how you could track those activities. They may come up with some good ideas, or at least get a better understanding of your situation.
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The trouble with doing something right the first time is that nobody appreciates how difficult it was - Steven Wright