In addition to total cost, it is useful to calculate cost because it can be compared directly to the price

It seems like your question is incomplete. However, I believe you're referring to the "unit cost" or "average cost".

Here's why it's useful to calculate:

1. Identify the cost: The first step is to identify the total cost of production. This includes both fixed costs (like rent and salaries) and variable costs (like materials and direct labor).

2. Calculate the quantity: The next step is to calculate the total quantity of goods produced.

3. Divide total cost by quantity: The unit cost is calculated by dividing the total cost by the quantity of goods produced. This gives you the cost per unit of product.

4. Compare to price: Once you have the unit cost, you can compare it directly to the price at which you're selling the product. This helps you understand if you're pricing your products profitably.

5. Make adjustments: If the unit cost is higher than the price, you're making a loss on each product sold. You'll need to either find ways to reduce your costs or increase your price. If the unit cost is lower than the price, you're making a profit. You could consider whether there's room to reduce your price to increase sales volume, or whether you can invest more in increasing production.