Visa、Mastercard 及多家美国大银行因信用卡交易费涉嫌垄断遭集体诉讼

You've got it backwards, their anti-competitive practices is what allows them to charge such high fees:

> A class action lawsuit alleges Visa, Mastercard and some of America's largest banks have conspired to artificially inflate merchants' credit card transaction fees.

If they didn't conspire together and actually competed then they wouldn't be able to charge such high fees as they would surely try to undercut each other.