There is no difference in pricing for our BigCommerce customers. You will only be charged transaction fees on purchases that flow through PayWhirl widgets or payment forms.
Any transactions that flow through the normal BigCommerce cart will be separate and will not be charged PayWhirl fees and visa versa. Any transactions that flow through our cart will not be charged BigCommerce fees.
When purchases do flow through PayWhirl widgets you will be charged PayWhirl transaction fees (0.50% - 3.00% depending on your plan). This is in addition to the merchant & processing fees charged by the Payment gateway you connected to PayWhirl.
Please let us know if you have any questions.