I hope this document helps you to calculate the AWS S3 usage cost for your use case.
Disclaimer: the plugin author is not responsible for your unexpected expenses.
Make sure to consult the pricing for your region here!
helm s3 reindex <repo> command is much more expensive operation than other in
this plugin. For example, reindexing a repository with 1000 chart files in it
results in 1 GET (ListObjects) request and 1000 HEAD (HeadObject) requests.
Plus it can make additional GET (GetObject) requests if it did not found
required metadata in the HEAD request response.
At the moment of writing this document the price for HEAD/GET requests in eu-central-1 is $0.0043 for 10 000 requests.
So the whole reindex operation for this case may cost approximately $0.00043 or even $0.00086.