In this work, we focus on using pricing as an incentive mechanism to encourage self-interested access points to participate in a public wireless network. Specifically, we employ a centralized model to aggregate all of the access points deployed by different businesses into a federated market, enabling wireless clients to select the cost-effective access service with the consistent quality. The proposed pricing scheme is based on a second-price auction protocol. In addition to the cost-performance concern on the wireless access service, a travel-expense is introduced as another concern to the wireless clients for the service selection among different access points. Finally, we show that the proposed scheme outperforms a fixed-rate pricing scheme in terms of network utilization and resource allocation efficiency via simulation.