Various embodiments determine a dynamic price of a first item for sale via an attached first smart price tag. The back-end price server receives a request for a current price of the first item for sale and a representation of a user signature motion from the first smart price tag, the first smart price tag associated with the first item for sale. The back-end price server determines the current price of the first item for sale for a user profile handle mapped to the user signature motion. The current price of the first item for sale is sent to at least one of the first smart price tag or a mobile device associated with the user profile handle. The request for a current price of the first item for sale is initiated by shaking the first smart price tag using the user signature motion.