Does aws charge for ThrottlingException on dynamodb request ?

For items which are returned in UnprocessedItems you are not charged for them, but you will be charged when you retry these items:

Throttling prevents your application from consuming too many capacity units. When a request is throttled, it fails with an HTTP 400 code (Bad Request) and a ProvisionedThroughputExceededException. The AWS SDKs have built-in support for retrying throttled requests so you do not need to write this logic yourself. Read/Write Capacity Mode.

Its important to note that you do write the logic for retrying BatchWriteItems when being returned UnprocessedItems, therefore, you should ensure you use exponential backoff and retry mechanism as this will reduce the amount of throttling you are seeing.

No, as per Read/write capacity mode - "Throttling prevents your application from consuming too many capacity units. When a request is throttled, it fails with an HTTP 400 code (Bad Request) and a ProvisionedThroughputExceededException"

Basically in dynamodb side you are not charged but for network throughput you will be charged

Knowing that all internql inbound throughput is free si just cobsider using dynamodb endpoint to keep your calls internal,

By the way, you need to look more global if you need to caculate your charges