The available size of Aura Database and its cost is displayed when you click on create database option in the console page.
You will see the different sizes and resources available along its cost details.
The updated pricing details can be found here: https://neo4j.com/cloud/aura/pricing/
A database priced at $0.18/hours will cost you 24 hours x $0.18/hours * 30 days = $129.60 per month.
Please refer below link for Billing FAQs: https://aura.support.neo4j.com/hc/en-us/articles/360037061854-Neo4j-Aura-Billing-FAQ