I assume they meant merchant fees.
But we are well past my economics understanding.
Visa: https://www.visa.ca/en_CAsupport/small-business/interchange....
Mastercard: https://www.mastercard.ca/content/dam/mccom/en-ca/Documents/... (PDF)
AMEX is a bit harder to find, reseller is https://www.helcim.com/ca/american-express/