But even though the marginal cost of admitting additional users is zero, the cost of providing the facility is not. This cost must be covered somehow, and it must be determined how large a facility should be provided. With exclusion inappropriate, even if feasible, the task cannot be performed through the usual market mode of sale to individual consumers. Provision through the market cannot function and a political process of budget determination becomes necessary, a process which permits consumers to express their preferences through the political process and also obliges them to contribute.