There are pricing in the "Green Sheet" farm newspaper, that serves Mn, SD, ND and most of the buildings are between $7.20 - $8 bucks a sq ft. They had sizes from 30x40x12 up to 70x140x18. The smaller the sq footage, the more it cost. I was supprised, figuring the wider would cost more.
The best price was between 50-60 ft wide and 16ft tall. Wider cost a few more cents per ft more and taller )18-20ft )kicked up the price a few cents higher.
That's building shell - no concrete or finished inside
Edit: That would be wood pole construction