I've been using per opening prices for many years. It has worked out quite well. These prices get tweaked and can get bumped up depending on job site conditions. Better than sq ft pricing because it takes into account what the openings that are actually getting installed. Its weakness is in jobsite conditions. But if you note things like that a dedicated circuit that has to be run a long distance, you can adjust that number specifically.
There is a little bit of "dartboard" in any pricing method. To predict what the job will actually cost is every bit of predicting the future. It is really no more than an educated guess. The educated part is the part that keeps you from losing the house, whether all at once or brick at a time.
When pricing something I have not done before, I think through every detail of the job and guess how many man-days it will take and throw a little bit more on for problems. But I often think how risky this business can feel when you imagine all the things that could go wrong.
