I think what AMEX is doing here is just making sure that Revolution does not cannibalise the AMEX business. They can sort of control which merchants revolution

I think what AMEX is doing here is just making sure that Revolution does not cannibalise the AMEX business. They can sort of control which merchants revolution is accepted at, by carefully aiming their marketing efforts and offering different businesses different deals. Thus, they can target revolution only at those stores that do not accept AMEX because of their high fees. So they can have revolution undercutting visa/mc but not undercutting AMEX.