Agile is not the most efficient or cheapest way to deliver a project

Let's get one thing clear. Working in an agile manner should be the case whenever the end deliverable or the overall scope is not known at the beginning of a project. However, this approach requires some ring fencing of people and resources, so it's not the most efficient or cheapest way to deliver. We need to be aware of both the benefit and the cost side when deciding on the approach. There is always a tradeoff to consider!