How much of the cost of housing is construction vs land costs, utility hookups, developer profit and permits? Tiny houses are relatively energy inefficient (a lot of wall surface for the living space), inefficient in land usage and very expensive per square meter. And they are not suited for families with children. I wonder if these trade offs are worth it against building a reasonably sized prefab home.

What would you say differentiates a tiny house from a trailer set up in a trailer park? And from a tiny house estate to a trailer park?

Sure, it's cheaper to construct utilities on a per-unit basis in dense areas. The problem is that in medium-density areas the utilities were built out decades ago and are near capacity now. So, in order to add more housing units and residents in a neighborhood they have to rip out and replace many of the utilities. This is extremely expensive, and disruptive for existing residents.