When building a closet, the existing walls need to be moved and new lights have to be installed. All this work requires numerous hours of labor, besides the cost of material supplies. The cost of materials will be approximately $1,700 and the labor cost will be about $1,000, making the total cost of building a closet $2,700. However, if the side walls are omitted, the cost falls down by about $500. If more lights are installed and if the interior decoration is done on a large scale, then the total cost will increase by at least 40-50%.