This resource allows you to estimate the up-front costs of digitisation work. Enter the staff costs of people working on your project and, as well as image-capture, you can factor in other processes such as quality-checking and creating metadata.
(Ignore that the default currency is US$. There is no need to do any conversion and you can just enter the costs in your own currency.)
Click the link on the right-hand side to view the resource on the Digital Library Federation website.