Cost modeling for construction projects usually focuses on the owner's perspective, but this study looks at it from the contractor's point of view. By analyzing data from 13 residential and 10 office buildings, the researchers developed models to estimate costs early on in a project. They found that factors like above and below ground areas, the years after the 2008 financial crisis, and the number of underground floors significantly impact cost estimation and deviation. The study also identified a correlation between cost deviation and the number of underground floors in office buildings.