The actual answers to OP's question is that management needs to know: - how much resource to allocate to the task - variations of the estimates in function of

The actual answers to OP's question is that management needs to know: - how much resource to allocate to the task - variations of the estimates in function of variations of the scope In my experience, "ballparks" estimates are sufficient for this exercise, and precise estimates are just resource-tracking leading to the issues described by OP.