I love this project and don't want to disparage the work that goes into it, but 900 USD, and it has to be a book that is already transcribed online? That seems a bit much to me.
That sounds quite reasonable to me. That's about what a freelance proofreader charges to edit a book, if https://thewritelife.com/how-much-to-pay-for-a-book-editor/ is correct, and that's working with a (likely Word) document which isn't poorly scanned from paper.
