The usual rates quoted would be in line with those advised by the Society of Indexers; i.e. £23.00 an hour, £2.55 a page or £6.95 per thousand words for an index to a straightforward text.

However I am happy to consider set fees if appropriate, and will take into account factors such as the intended market and intensity of the text, numbers of pages and illustrations, deadlines, etc. 

For more information on Fees and Charges for indexes, please see https://www.indexers.org.uk/index.php?id=135 (Fees for Indexing: Guidelines for Clients) on the website of the Society of Indexers.