The invention relates to a quantity-price cost monitoring system comprising a system body and a power supply device. A power supply circuit is arranged in the power supply device in a built-in manner.A +5V power supply in the circuit is grounded through a capacitor C25 and is connected with a D pole of a transistor Q1 through an inductor L1; the inductor L1 is grounded through a capacitor C24, isconnected with an INN port of a chip U7 and is connected with a resistor R81; the resistor R81 is connected to the ground via a capacitor C12 and is connected with a VIN port, an ENP port, a PSP port, an ENN port, and a PSN port of the chip U7; an AGND port and a GND port of the chip U7 are grounded at the same time; a G pole of the transistor Q1 is connected to a chip BSW port; an S pole of thetransistor Q1 is grounded via a capacitor C32 and is connected with an INP port of the chip U7 through an inductor L2. According to the invention, the designed power supply circuit inputs stable powerin the system to prevent the impact on the system circuit by the surge current in commercial power and thus avoid the circuit damage.