You are charged for the parts that are generated during multipart upload based on the storage class, actual size, and storage duration of the parts.
Billing rules
The storage class of the parts is the same as that of objects. However, the parts do not have a minimum billable size. If a part is less than 64 KB, it is still calculated based on the actual size.
For more information about the storage fees for parts, see Storage fees.
Suggestions
To avoid additional storage fees caused by parts, you can use one of the following methods to delete parts in a timely manner:
Manually delete parts
For more information, see Delete parts.
Automatically delete parts
You can configure lifecycle rules to delete parts. For more information, see Configure lifecycle rules to delete expired parts.