How Is RDS for MySQL Backup Data Charged?
All the RDS full and incremental backup data is stored in OBS. RDS provides free backup storage space of the same size as your purchased storage space. For example, if the storage space you selected when buying a DB instance is 200 GB, charging initiates only after the backup storage space usage exceeds 200 GB. The first 200 GB is free of charge for storage. The exceeded backup storage space is charged according to the OBS storage space tiered pricing.