This paper introduces a new cost based network planning approach where the main concern of the planner is decreasing the product unit cost rather than increasing the resource utilisation. The paper identifies inherent trade-offs in the network architecture that take advantage of the disparity between the cost of carriage components. Considering previous trends in the cost of hardware, software, and labour, the paper proposes a flat network architecture in accordance with the prevailing trend. It identifies the limitations of the current concept of ATM virtual paths in decoupling between the switching and transport utilisation. Consequently, it proposes a new approach to the operation of virtual paths called discordant virtual paths that enables maximum switching layer utilisation while maintaining an under-utilised transport platform. The discordant virtual path approach allows the network operator to adapt to variations in the cost of components. © 1998 IEEE.