That's appealing, but I'm not sure it is correct. My father spent his career designing power plants. His company had an estimation group tasked with estimating costs and schedules before they ever bid on a job. We're talking projects that could easily run over a decade and cost hundreds of millions of dollars. They did an internal study to see how well the estimators did compared to reality. When management didn't lean on them to shave down an estimate, they were really amazingly accurate.

Now, we're talking about a dedicated group of people who aren't going to do the work themselves and who do nothing but estimation, but still....