Wireless sensor networks have found numerous applications in realistic environments. Typically, such networks are desirable to operate in several years without human maintenance. Yet main radio components on the conventional wireless sensors quickly consume most of the limited energy in the sensors, and thus considerably constrain the sensor lifetime. Recently, many low-power wake-up radios are designed and engineered in the industry. They can reduce energy consumption of the wireless sensors. This paper investigates the minimum cost deployment problem for wireless sensors with wake-up radios in practical deployments, where conventional sensors, independent wake-up devices, sensors with conventional and wake-up radios are all taken into account. Our investigation opens a promising way for wireless sensor networks reaching much longer lifetime in the minimum financial cost.