Server

For the Server version of this app, please refer to this list: https://marketplace.atlassian.com/apps/1219932/language-translation-jira-service-desk?hosting=server&tab=pricing

For Jira, you must purchase the add-on license that matches the highest Jira application tier. For example, if you have a 500-User Jira Software license, and a 20-Agent Jira ServiceDesk license, your Jira add-ons must be at the 500-User level. 

https://www.atlassian.com/licensing/marketplace#licensingandpricing-1

Jira Service Desk portal users (customers) do not consume a license at all.
So if you have 10 Agents in Jira Service Desk and 700 users are using the portal only, you only need a 10 user license of the app.

Another mixed example: If you have 10 Agents in Jira Service Desk & 100 users in Jira Core as well as 600 portal only users,
you need a 100 user version of the app, as it is the highest Jira application tier (see quote from Atlassian above).

Cloud

To calculate the price for the Cloud version of the app, please user the calculator from Atlassian: https://www.atlassian.com/software/pricing-calculator

1. select choose your cloud product first, i.e. Jira Service Desk
   
2. select the right plan, enter the amount of agents and click on the Any apps?
   this will reveal an app lookup field in which you just need to type Language Translations and pick our app:
   
3. the calculator will show the price for the app as well: