Nothing really wrong with bidding new work per opening The problem is when you disclose that information to the public. When I used to run new construction jobs, I was bidding per opening. It made estimating a snap, but no where in my bids or contracts did you see a dollar amount other than the total at the bottom. I don't need a direct comparison to another company. "Well ABC's price for a GFCI was $66 will your's is $168, while your can price is $100 and ABC's is $200, I want you to match the his price only when his is lower than yours." Devices had one cost, ceiling boxes, exhaust fans, cans, furnaces, all had different numbers, but it beat doing a take-off on each and every item.
And yes per opening would cover all of this " Boxes, devices, wire, labor, profit ?" at least it better