This disclosure relates to system, method, and computer program for providing a wish-list user interface within a web browser, for tracking “fully-stacked prices” for items in the wish list, and for alerting users to a drop in a fully-stacked price of an item in the wish list. A browser extension provides a wish list user interface within a user's web browser. Via the user interface, a user is able to add products from different merchant websites to the wish list. As each item is added to the wish list, an initial multifactor-based price (i.e., the fully-stacked price) is calculated for the item. While an item remains in the wish list, a backend server continues to track the multifactor-based price for the item. In response to detecting a drop in a multifactor-based price for an item in the wish list, the browser extension alerts the user to the price drop.