In theory, yes, it is (cost + profit / number of shoot ) that determine what you need to charge per shoot.
In real life, the charge depends on the market condition, your clientele as well as the perceived value of your work.
Simple equation is If
Value > Price, you will sell a lot
Value = Price, you will sell at normal pace
Value < Price, you will sell at very slow pace or no sale at all.
You can always adjust your value by keeping the price the same to move from one category to another. I find that adjusting value is better than adjusting the price.
This is unfortunately the real life of it. Real life isn't as pretty as many will think and real life isn't linear equation either...
Sometimes, in the beginning, you charge at a rate just barely cover your basic cost + profit to get by, but if that is your value is, then you need to start increasing your value. Sometimes, as start, you do have to go negative to get some leads to move forward. Although the motivation of a business is always profit, sometimes it is better to lose some money in the beginning.
For example, you will need to spend money for advertising before you even get any job. Many don't want that, and every one think that they should make money from day one. Unfortunately, unless you are so talented and the whole market like what you do, then this is not a luxury that you have.
Go and digest.
Regards,
Hart