But how much to they really save just by having a half-height corridor? Is it really more than a short corridor with CG extensions? And surely it's cheaper to film in front of a real barn, rather than model a mini one. Or is it? This is crazy!
You're saving half the supply cost at least as well as labor and the post-production costs of adding the CG extensions. Much more economical.
As far as the barn goes, maybe they didn't have one nearby or in the appropriate style.
Yup, and not only that, but you completely control the look of the building, it takes much less time (besides MUCHO less expensive) and you can place it wherever you need it for the light you're shooting it with that day. Much more trouble and $$$ to redress an existing building, plus the hassle of lighting it.
I've been an extra too - Eight Men Out and Continental Divide. And one other. Can't see me, I'm in crowd scenes.