I think they were saying that the time and hours taken is not commensurate with the purchase cost, not proposing it as an actual solution. That said I think they are still very wrong.
If you were to build a modern house from scratch, you're taking enormous amount of time. Imagine felling the the timber and Milling it alone would take years. Ignoring the material side of things, most of what you're paying for is the knowledge and experience of the laborers. It takes a lot of time to learn each trade and how to build properly. It also takes a fair amount of work to learn the the regulations and comply with the certifications for each task