During post-earthquake reconstruction, the traditional method used to determine the lowest cost of buildings is unable to balance the relationship between costs and construction requirements, which ultimately results in low-cost buildings with low seismic capabilities being built. This study proposes a method for analyzing the lowest-cost required to re-build following earthquakes. The relationship between building cost and demand is analyzed, and basic data are provided. In addition, the IFC building standard is optimized and lowest-cost indexes are defined. Furthermore, analysis factors are comprehensively determined to balance the demand relationship in the value chain. Finally, a lowest-cost analysis model for buildings is presented. Experimental data show that the lowest-cost analysis model not only meets the demand relationship but also realizes the lowest-cost for buildings.