When you create an option value, you can enter a price modifier and a weight modifier (in default currency). In this way, an option selection by a customer can change the overall value of an item. For example, a T-shirt might be €14.99, but the extra-large option might be €2.00. When the customer selects this option, the price of the T-shirt on the page will change to €16.99.

Similarly, a particular option that adds additional weight can be accounted for (important if your shipping prices are related to item weight).