How can initial and whole life costs be controlled on a project during the design stage?

The initial project cost remains an estimate, of increasing accuracy until project completion. The whole life cost estimate will increase in accuracy as the project develops. The accuracy of both of these estimates is dependant on the stability of the project scope and the effort invested in deriving the estimate.How can initial and whole life costs be controlled on a project during the design stage?
BY getting the design right, and building in contingency to the plan.