For every credit or debit card that is issued, there is a rate established by the card associations that is collected from the merchant. Interchange rates are made up of two different components: a percentage fee for the volume of the sale and a per-transaction fee. These rates will vary depending on the type of card, how the transaction is processed and your average transaction volume. In addition to interchange rates, the card associations may charge a separate assessment fee which covers the operating cost of their network. Interchange rates apply to all merchant service providers, such as TransFund, and we all have the same interchange costs. Interchange and all related assessment fees are based on current published rates from Visa, MasterCard, Discover and American Express.

https://usa.visa.com/support/small-business/regulations-fees.html

https://www.mastercard.us/en-us/about-mastercard/what-we-do/interchange.html