This article examines cost behaviour in a municipal (local government) setting and finds evidence of cost stickiness. We also find that costs are super-sticky as they increase even when revenues decrease. Municipals in New Zealand are required to produce forecasts, which allow us to investigate whether asymmetric cost behaviour is incorporated into forecasts. Forecast cost behaviour is found to be statistically indistinguishable from actual behaviour. In our tests, we control for asset intensity, employee intensity, expected demand, operating slack and past cost structure. The finding that the asymmetric relation between costs and revenues is incorporated into managerial forecasts suggests that cost stickiness is understood by managers rather than being merely a mechanistic outcome of cost structure.