Cost VS time is not the real question. It is faster and cheaper to buy frozen doughballs, for example. The real question, as stated by La Sera, is if fresh mozzarella is something you want to do as a feature or a way to save money? It is doubtful you will save money or time by making good dough, fresh mozzarella or sourcing local produce, but unless you plan on using minimum wage workers with a conveyor oven, then the extra cost and time should simply be accounted for and marketed as such to differentiate your business from the common run of fast food.