In Settings – Products you can specify how should the total price be calculated.
In the pop-up window, there are 5 columns: Name, Price, Quantity, Discount, Tax.
Under this column, you will select all the fields that you have values assigned. At the top right of the window click the + sign to add more.
The price column will auto-detect its type based on the field’s functionality. There are three types of values:
Click the price type. This will allow you to change the prices or to assign values to your choices.
Note that formulas can not be modified from here. You will need to return to your formula field to bring changes.
By default, each product is multiplied with 1. However, you can choose another number field.
In the first column select a choice field and under Quantity select a number field where users inputs their desired number of products.
Important note For each choice field you will need another number field for the quantity input.
In each field, you can apply a discount and a tax. You can choose a percentage or a fixed value.
If you are using another version, check out this article with the same subject.