Why are air-supported structures cost-effective for very long stadium spans?

Pneumatic structures, specifically air-supported membranes, are considered perhaps the most cost-effective building type for very long spans because they utilize internal air pressure rather than heavy, rigid materials to maintain their form.12

By increasing the internal air pressure slightly above normal atmospheric pressure—often by as little as 1.5 percent—the structure is able to support itself. This system relies on a lightweight fabric membrane stiffened by a network of cables, which is anchored by a rigid compression ring at the edge. Because the air pressure provides the primary support, these structures avoid the high material and construction costs associated with the heavy steel trusses or complex grid systems required for traditional long-span roofs. Additionally, the system is efficient to maintain, as relatively small compressors can sustain the necessary pressure even in large buildings.12