  We analyze analytically the effect of congestion costs within a physically
relevant, yet exactly solvable network model featuring central hubs. These
costs lead to a competition between centralized and decentralized transport
pathways. In stark contrast to conventional no-cost networks, there now exists
an optimal number of connections to the central hub in order to minimize the
shortest path. Our results shed light on an open problem in biology,
informatics and sociology, concerning the extent to which decentralized versus
centralized design benefits real-world complex networks.
