Shopify charges additional surchage fees for payments done through any third party payment gateways like HitPay.
For further information, you may refer to the below link:
The additional charges imposed by Shopify depends on your existing subscription plan with Shopify. Please refer to Shopify's pricing plan for additional transaction fees charged by Shopify for payments done through third party gateways.
Below is an example of the total fees paid by Shopify merchants in Singapore for PayNow transactions.:
