One charge, one office, one act
Most anxiety about legalising a paper abroad is really anxiety about open-ended cost — the sense that each stamp invites another. On a treaty route that worry has nowhere to attach. There is a single national office, a single published rate per sheet, and a single act at the end. Once the marked paper is back, the spending is over.
India inside the Convention
India joined the Hague Apostille Convention in 2005. Since then, document legalisation for India has meant one slip in the shape member states agreed on, accepted without any further examination at the far end. The absence of that examination is exactly what removes the second fee, because the second fee always pays for somebody reading the file.
The Wolverhampton to India route in practice
An apostille issued in Wolverhampton for use in India is actually produced in Milton Keynes, since one office covers the whole country and deals with everything by post. Nothing about the marking stage happens locally. What does happen locally is the making of the record, and the register office at the Civic Centre holds the civil entries for this city and prints signed copies of them.
So the practical plan is short. Work out which records the Indian side has actually named, order signed versions of those, send them together and wait for the envelope to come back. There is no queue to join afterwards and no separate desk to satisfy, which is why this road is easier to cost than to time.
The part that is not published
Timing is the item nobody prints. The examination itself is brief, so the wait is dominated by the two postal journeys either side of it, and the next-day service shortens only the middle. A paper tied to a fixed date in India should therefore leave this city earlier than the published figures alone would suggest.