The cost to accept credit card payments depends on the amount of the transaction being processed.
But let's take for example. If you sell something for $100.00 and someone uses a credit card to purchase the item you will be charged around $2.50 to $3.00 per $100.00 credit card transaction.
This is why I understand when someone wants to charge me a fee at the register to use my credit card and especially for a small business.
It cost the merchant money to get their money from you through a credit or debit card.