The steel and concrete have the same materials cost as steel and concrete for ground mounted panels.
The large scale members usually mean there is less labor cost and mobilization time, and hence overhead (insurance, fencing, trailer, etc.). Like I said pre-engineered metal buildings are about the cheapest cost per square foot you can get at scale.
The raw material cost for steel is by the ton. Barring unusual circumstances. And metal bents are very very structurally efficient.
Incidentally, they are not “I beams” and technically I-Beams are Wide Flange Shapes and used vertically as well as horizontally, and designated with as W(n)x(m) where W means wide flange, n is the depth in inches, and m is the weight in pounds per lineal foot. W shapes are rolled in rolling mills.
Bents are fabricated from steel plates to a design specific to the structure.
The large scale members usually mean there is less labor cost and mobilization time, and hence overhead (insurance, fencing, trailer, etc.). Like I said pre-engineered metal buildings are about the cheapest cost per square foot you can get at scale.