This paper provides a simple mechanism for cost optimal construction of irregular networks based on three criterions: (1) Distributing the nodes over the switches in such a way that the resulting link utilisation is balanced (when assuming a uniform traffic distribution); (2) using as small number of switches as possible; (3) using the smallest possible switches. This is assuming no parallel links as these will add additional ports to the switch without helping the connectivity. Our construction then gives cost optimal network topologies up to a limiting switch size. This provides insight into the influence of the switch size on network cost.