We present a mechanism for trading database tuples in a multiagent system. The mechanism enables negotiation and evaluation of database-based information goods. As part of the work we propose various policies for dynamic pricing of information goods. We have developed a test-bed that simulates a multi-agent system where agents use the offered mechanism and evaluated the system performance when sellers use different pricing policies in competitive and non-competitive environments. The investigated pricing policies include two novel pricing policies that implement negotiation and price discrimination across buyers. These were compared to two policies known in the art, which implement dynamic posted pricing. We have empirically demonstrated the superiority of the offered policies in maximizing sellers' gains. We have additionally identified equilibria profiles of these policies.