How do I determine my server pricing?

Apps are billed based on the number of users in your Atlassian product. The app tier should match the licensed user tier of the Atlassian product. For example, if you have a Confluence license for 500 users, you should purchase the 500-user tier for apps. Even if fewer users want to use the app than your Atlassian product license, the two licenses should match exactly.

Source: https://marketplace.atlassian.com/apps/1212995/staffing-timeline?hosting=server&tab=pricing

Feel free to tell us what topic should be covered: staffingtimeline@psc-software.atlassian.net