Using BrickSeek when you are in store to verify price at a price scanner
While on the Inventory Checker page click the "View Barcode" button as seen below.
Once you click "View barcode" the following image will appear. Simply hold that barcode under a price scanner in store. You will then know the price of the item. If your seeing a different price appear when you scan the item as opposed to when you scan your phone, that means the UPC codes do not match, thus you do not have the correct item.