Not all electrical wires are created equal. In fact, the cost of cables depends on the size, length, insulation thickness and material, and brand. The cost increases exponentially with the size of the conductor. Usually, the size of the conductor refers to the thickness of the copper conductor inside the cable and not the entire cable itself. The more weather protection a cable has, the more it will cost. In order to estimate the cost of the wiring materials, you will have to figure out what type of cable you want and its length.