On a very general level you will be billed on a usage-based pattern, based on the queries executed against the SQL warehouse underneath - meaning the more questions, and the more complex they are, the higher the cost.
The below topic has a reference as well as a little bit more context provided by @MoJaMa that you might find useful.
Modelling Genie AI/BI costs
TLDR; Think about the realistic number of users, and the corresponding number of sessions/queries.