Our on-premise edition comes with a perpectual license and is priced by number of support agent users, starting at $79.99 for unlimited end users and 1-support agent. Our SaaS edition is also priced by number of support agent users, starting at $19.99 / support agent / month, with increasing discounts for more support agents.
Prices are based on a one time setup cost and an annual subscription which will cover all the functionality.
You will not incur other costs for upgrades, backups, data store etc.
You will simply need an internet connection.