Commerce Price Savings Formatter achieves a very demanded and useful feature for managing Drupal Commerce prices, it displays the original price of the products crossed and enhances the discounted price, displaying the amount and percentage that the customer would save if they purchase the item. All those components are optional so you can choose which to show in your prices.

The module uses a display formatter for doing all these operations so it can be used both in the display fields configuration screen and in Views. Oh, and it is also VAT safe, which is a great thing.