Pirate Ship offers USPS shipping with discounts up to 87%, making it a great...

https://papa-wiki.win/index.php/Shippo_vs_Pirate_Ship:_Which_One_Has_Better_Integrations_for_Marketplaces%3F

Pirate Ship offers USPS shipping with discounts up to 87%, making it a great choice if you mainly ship domestically and want big savings. Their email-only support can be slow, though