There are, and both Visa [0] and MasterCard [1] have both recently been in trouble for it. Instead of it being a specific maximum, however, it must be "reasonable" and allow for competition. The network also chooses the cheapest routing, by default.

[0] https://www.accc.gov.au/media-release/visa-undertakes-to-add...

[1] https://www.accc.gov.au/media-release/mastercard-in-court-fo...