Payment gateway providers are not always transparent about their EFTPOS card machine prices. Each payment may have different fees associated with it and it’s not always clear why those fees are (or aren’t) applied to a given transaction.
In addition to a per-transaction percentage, many payment gateway and payment processing providers charge all or some of the following:
Monthly account fees
Membership fees
PCI-compliance fees
Initial setup fees
Batch fees
Refund/chargeback fees
Higher rates for cards like American Express