The advisory cost limit was last increased in 2000, Official Record,
The purpose and application of the advisory cost limit remains unchanged. It is intended to act as a threshold for disproportionate cost parliamentary questions (PQs). Any written PQ where the marginal cost of preparing the answer is considered likely to exceed the threshold may be refused in whole or in part on the grounds of disproportionate cost. Alternatively the Minister may decide that the PQ is to be answered irrespective of cost. There is no advisory limit for oral PQs.
The advisory limit continues to be based on eight times the average marginal cost for written PQs, which is now £75, rounded down to the nearest £50 for convenience of application.