Motivated by recent regulatory evolutions that pave the way to secondary spectrum markets, we investigate profit maximization in a loss network that accommodates calls of two classes of users: 1) primary users (PUs) and 2) secondary users (SUs). PUs have preemptive priority over SUs, i.e., when a PU arrives to the system and finds all channels busy, it preempts an SU. We assume that SU demand is sensitive to price whereas PU demand is inelastic. We study the optimal pricing policy of SUs to maximize the average profit by introducing a finite horizon discounted dynamic programming formulation. Our main contribution is to show that the optimal pricing policy depends only on the total number of users, i.e., the total occupancy. We also demonstrate that optimal prices increase with the total occupancy and show that the optimal pricing policy structure of the original system is not preserved for systems with price-sensitive PUs. Finally, we extend the results to non-preemptive loss systems and establish a connection with results obtained for such models in the literature.