Hi, here I will explain to you how to determine your server pricing tier.
The add-on tier should match the licensed user tier of the Atlassian
host application. For example, if you have a Confluence Server license
for 25 users, you should purchase the 25-user tier for add-ons. Even if
fewer users want to use the add-on than your host application license,
the two licenses should match exactly.
Here the link to the pricing for draw.io: