Auctions and exchanges are important coordination mechanisms for multiagent systems. Most multi-good markets are combinatorial in that the agents have preferences over bundles of goods. We study the possibility of determining prices so as to support (efficient) allocations in combinatorial economies where a seller (or arbitrator) wants to implement an efficient allocation and the prices are required to be anonymous. Conditions on the existence of equilibria are presented and a particularly attractive pricing scheme is studied in detail. The relation of minimal equilibrium prices to Vickrey payments is analyzed. A procedure based on the controlled formation of alliances is suggested that shrinks economies to ensure the existence of prices coherent with the preferred pricing scheme.