1 In general, you can expect to pay approximately $15 to $25 per square foot for a basic rigid frame commercial steel building (all inclusive). 2  More customized/refined commercial metal steel buildings might cost closer to $20 to $40 per square foot. $10,000 to $12,000 for a 20 x 20 rigid frame commercial steel building and $6,000 to $8,000 for a 20 x 20 arch frame commercial metal building.