Question

what is the best method of preparing realistic cost estimates?

Answer 1

Bottom-up Estimating Method is considered as the most realistic cost estimate method

In the Bottom-up estimating method, team and physical resources are estimated at the activity level and then aggregated to develop the estimates for work packages, control accounts, and summary project levels.

Bottom-up estimating is a method of estimating a component of work. The cost of individual work packages or activities is estimated to the greatest level of specified detail. The detailed cost is then summarized or rolled up to higher levels for subsequent reporting and tracking purposes