Re: AMEX not accepted or surchage
I got that offer too but after 3 years it was to go back to the original rate.
Never mind the TPA, but under the rules that allow sucharging, the RBA left it up to the acquirers (the banks/Amex) to enforce limitations on how much a merchant can surcharge. So, I would say, under the framework that the RBA devised, it is the entirely appropriate mechanism for Amex to use.
If the Amex merchant rate is the same as the Visa/MC rate, then it seems a reasonable restriction for Amex to impose.
I got that offer too but after 3 years it was to go back to the original rate.