Embodiments of task-based, decreasing-price markets enable dynamic discounting of items for sale. In one example, users shop for products (e.g., clothing, electronics, or cars) or services (e.g., hotel rooms, plane tickets, or car rentals) using a computing device or mobile device. As the users shop, they view advertisements or perform other tasks, like answering questions, and the system discounts an item's price based on the number or complexity of the performed tasks. Each user who performs a task gets a chance to buy the item at its discounted price. The other users also get a chance to buy the item at the discounted price. If someone buys the item, the item's price returns to its starting value. If nobody buys the item, the system discounts the item's price further as the users perform more tasks until someone buys the item or the item's price reaches a minimum value.