Some vendors have a minimum starting tier for purchasing "per account" licenses. For example, even though I only want 50 user account licenses, I may have to purchase 100. Just wondering if Splunk has a such a minimum for the Splunk UBA app.
This may help:
https://docs.splunk.com/Documentation/UBA/4.0.2/Install/DeploymentArchitecture#Scaling_your_deployme...
Also you can contact splunk sales team regarding custom requirement.