In general, the average cost to make a 14” American Pizza is, I would imagine, going to be pretty cheap considering that the average pizzeria makes a poor product.
Are you making pizzas already?
Step One: get a scale.
Put some cheese in a container. Weigh it.
Put some sauce in a container. Weight it.
Put whatever other toppings you want in an individual container. Weigh them.
Make a pizza in the manner you prefer/plan on making them (sauce amounts, cheese amounts, etc). When done making the pizza, weigh the containers again. The difference is how much of each ingredient you just used. From there it is easy to figure out your cost because you already know the cost you are paying to a wholesaler, a specialty shop, a farmer, etc for a particular item.
For items like flour, water, salt, etc, use one of the Dough Tools available here (
http://www.pizzamaking.com/dough_tools.html) to find out how much of each ingredient it will take to make a pizza. Use the cost it takes to obtain these items on your end to determine your ingredient cost.
Good luck. --K