Why one price never covers this route
Qatar has not joined the Hague Apostille Convention, so a British mark on its own does not settle a paper used there. Papers headed that way need embassy or consular legalisation instead: certification by the FCDO Legalisation Office first, then a consular stamp laid on top of it. Two desks, two separate charges, and only one of them prints a figure you could look up before you began.
Where Qatar stands
An apostille for Qatar is not the certificate that closes the job, and no wording on a covering note alters that. The position is fixed rather than a matter of local habit, so it decides how many desks touch your file and therefore how many times you pay. Settle it first and a vague budget turns into two lines you can plan around.
Two rates at the British desk
The Legalisation Office charges £45 / document for standard postal work, and £40 / document for a next-day line that is open to registered businesses. Read that pair again, because it runs the wrong way round: the quicker option is the cheaper one, and most people reading this cannot use it. A parent sending a birth record pays the higher figure and waits the longer wait.
The charge attaches to each sheet, never to the envelope. Three records in one package are three charges, so a family gathering papers for a single move abroad often finds the bill grows faster than the pile does. Working out how many sheets genuinely have to travel is the cheapest move on the whole route, and it costs nothing at all.
The charge with no printed figure
The consular stage sets its own fee and its own pace, and neither sits beside the British rates on any price list. Budget it as a real cost rather than a rounding error, and treat the £45 or £40 already paid as the part of the bill that came with a number. What you need for an apostille for Qatar is the wrong thing to plan around; the useful question is how much of this route lies beyond the printed figures.