First, the cost of materials: To do any electrical work you will need to buy a wide range of high-quality materials. These materials include wire, conduit, junction boxes, and light fixtures. These costs can quickly add up, especially if you're working on a large project.  Second, you may also need to hire apprentices or helpers depending on the size of your project. These can add hundreds of dollars to the final cost. This is done to make sure everything was completed according to code. Any problems that are discovered will need to correct, which can increase the cost.