Papers have traditionally been published in MNRAS with no page charges for the authors. However, the rapid increase in the number of submissions in recent years, and the rise in the total number of pages published per annum -- with its cost implications -- have led to a reconsideration of this policy.
The RAS has taken the decision to introduce a charge of £50 per excess page for papers over 20 published pages -- which leaves unaffected about 90% of currently published papers. The objective of this change is to limit the total number of pages published per annum, and not to provide an additional income stream.
In practice, many submissions that would exceed the 20-page threshold could, with a little reorganization, be reduced to below the threshold, notably by the appropriate use of supplementary online material, for which there is no charge.