A computer-implemented method includes receiving item data at a network-based computer system, the item data related to an item categorized in at least a first category of a plurality of categories supported by the network-based computer system and including an item price-based value associated with the item. A category-specific threshold price-based value, for the first category of the plurality of categories supported by the network-based computer system, is automatically determined. The item data is automatically determined to the irregular, based on the item price-based value associated with the item and the category-specific threshold price-based value for the first category of the plurality of categories supported by the network-based computer system. Responsive to the determination that the item data is irregular, an entity associated with the item is restricted from using the network-based computer system.