My RA interpreted more of the information from our Publication Office (I don't speak Japanese well at all) and I have learned that a budget request can be made for
(i) a standard page rate (which is arbitratry and based on writing fees paid to certain kinds of contributing author for certain museum publications), or
(ii) and expected cost based on a full quote by professional editor/translator or similar (indexing fits this category).
This means you can provide me with quotes based on your usual costing for the work, and then I can discover how much the museum is willing to offer. Our office has had some experience of indexing, but not with the help of professional indexers. I am keen to introduce the practice of professional indexing to our publications department.
Peter J. Matthews, Chief Admin.,
The Research Cooperative,
Auckland & Kyoto.
Contact: researchcooperative [at] gmail [dot] com