Junction box costs range from low‑price indoor models ($10‑$60) to weatherproof units ($70‑$450), with installation averaging $100‑$300 depending on location and materials. If you're planning any electrical work, one of the small but important items on your list will be the junction box. At first. How can we improve? Choose from our selection of junction boxes, including over 2,800 products in a wide range of styles and sizes. The main cost drivers are box type, material, weatherproofing, and any required accessories or adapters. The following ranges reflect typical U. prices for common residential applications. This guide focuses on practical cost estimates and per-unit pricing to help homeowners and. Get the latest prices and historical cost data in each U.