The more people that are in Kahootz, the less you will pay per user. To work out how much it will cost you, use the calculator in the application via Account > Site Admin > License Costs.
Additionally, on the License Costs page, you can renew your license from your site, which will send an email to our support desk.
Remember: we will not force you to buy bundles of user licenses. You only order what you need - if you need 47 user licenses then you order 47, not 50.