This system offers the best value for the money.
Not only the frames are factory-built, also insulation is fitted at the factory, together with external cladding, windows and sometimes even electric pipes and internal gypsum boards.

Some factories are able to deliver element walls, roofs, ceilings which are 80% finished in the factory!

Compared to on-site traditional building methods, this saves weeks and it comes with a  better quality.
In fact, all the materials are handled and fitted in a dry and controlled environment and there is no space left for last-minute improvisation (typical of on-site carpenter's work).

When you buy a prefab element house, you get exactly what you ask for.
Building with elements is smarter than building with frames.

Transport and handling costs are nearly the same while the work on-site is drastically reduced and the quality enormously increased.

Once elements are on-site, a two-story house can be assembled in a matter of days and made weatherproof in max 2 weeks.
Additional time (a few weeks) will be necessary to install technical systems and perform interior works and finishes. 

Almost any architectural solution can be developed using prefab elements.
If your house has a "weird" geometry, elements are the way to go.