The most important thing in negotiations is the starting point.
For example, laying out a book layout costs 2'000 euros and takes a month. This price includes 2 options of master layouts to choose from, light edits from the proofreader, and circulation of 1000 copies in one country. You will also need two meetings, the initial one to set up a brief, and the final one to sign the documents. You prepare the documents, and all correspondence is conducted remotely. The source materials remain with you, and you do the prepress. This is the starting point.