Machine-To-Machine (M2M) networks could be connected by a wide range of wireless technologies (e.g., Bluetooth, WiFi, RFID). The main goal of this paper is to explore efficient ways for the source to maximize the average delivery ratio when the total fees are limited. First, the authors mathematically characterize the average delivery ratio under different policies. Then, they get the optimal policy through Pontryagin's maximum principle, and prove that the optimal policy conforms to the threshold form when the fees that other nodes require satisfy certain conditions. Simulations based on both synthetic and real motion traces show the accuracy of their model. Through extensive numerical results, they demonstrate that the optimal policy obtained by their model is the best.