(11)To ensure that market data is provided on a RCB, the fees charged to clients belonging to a certain category should be set on the basis of the costs sustained to provide data to those clients and a reasonable margin, expressed as a percentage of costs, which should be homogenous amongst clients belonging to the same category. Market data providers should be able to charge different fees for different types of data (e.g. display and non-display data) on the basis of differences in the costs of production and dissemination of such types of data.