Price per opening
This way of bidding started back in the fifties, when the housing boom went in to high gear. The building developer would bid out piece work from all the trades. The idea was to find the lowest installed cost and get the highest price for the completed project. Before the housing boom, electrical contractors and others, would bid an estimated price, based on material and labor and then add a profit.
The price per opening, may have worked well, when all the homes were cookie cutter type.
Today, not all but some homes are larger, and have different electrical needs.
The builders use the price per opening to drive down the bid and cut the costs, so be sure your price will clear a profit when bidding price per opening.