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. Understanding distribution box cost involves examining the comprehensive investment required for electrical distribution systems that serve as crucial infrastructure components in residential, commercial, and industrial settings. At first. While distribution box prices depend heavily on capacity and features, we've tracked emerging patterns. You might find a small plastic unit for the price of a fancy dinner, or an industrial-grade stainless steel beast that costs as much as a compact car. The “how much” depends entirely on. Plastic junction boxes for indoor wiring cost 50% to 80% less than metal boxes but aren't as durable. Junction box installation is.