In your theory, if someone has given the best price possible and not allowing for any shaving off pennies, then you are working far too tight to begin with
If you are posting just to make a discussion its all for fun..
But. It is not theory. It is a basic law of economics.
It has nothing to do with running so close to the edge that shaving a few pennies blah blah...
As I posted above. Discounts are given only if it fits within the economies of scale.
That is an economic law. There is no changing economic laws. Run the business within the PLAN and MODEL.
Furthermore. In your case you are dealing with two different time patterns. Short run and long run.
The first run is doing one vehicle and it takes an amount of time including clean up and set up. After the first two vehicles the time is about the same over the rest of the run. However, that is a false economy. One is dealing with a short term measurement and the end of the run deals with a long term measurement.
The only saving that make any difference is the setup and clean up times. Once set up for production the actual time to complete a job will be mostly the same. Production time will average out to be the same over the long run. Thus no room for a discount.
The economies of scale work only when the long run allows more goods to be produced on a larger scale with lower costs.
Since the fixed costs such as materials, supplies, space and labor are all the same with a very small savings gained out of efficiency there is actually very little room for a discount.
There is always a "what if" variable. The "what if" variable makes for a good discussion but is usually not a genuine factor in pricing our products.