Do I get charged for duplicates?

No, you don’t use another credit for emails you already found in the last 30 days.

Duplicates leads will not appear in your “All contacts” page. However, if you scrape a lead within “list 1” and scrape it again when building “list 2”, then that same lead will appear both in “list 1” and “list 2” (but will have cost you only one credit total).