Moparmick -
We need to know what YOU understand "pre fab" to mean.
Alot of things labeled "pre fab" are not as pre fabbed as they make it seem, so I dunno.
Pre fab is usually a sales gimmick term.
Very rare exceptions to this, only like some garden gazebo kits or similar.
"Precut" is even worse.
They basically want to put a picture in your head that it's a very quick easily assembled erector set requiring a minimum of labor, hence you figure "O !! cheaper"
There is very rarely a free lunch, and never for buildings.
Closeout sales, whatever.
99.99% of times it's ********.
You have to pay for what you get.
Which is different from "You get what you pay for" cause you may, or may not.
Tell us what you want to end up with, and you'll get suggestions. Marc