Just experienced my first DCC terminal in Australia that's not in an airport. It was just at a tiny little restaurant in Melbourne which happens to have a brand new ANZ EFTPOS terminal. Exchange rate offered was .8184. XE gives the rate at present as .79934, so that's a fairly reasonable 2.33% markup. However, the AUD is rising rapidly at present, and Mastercard would only charge .786, making DCC 4.12% more expensive.

Of course, users have to hit "cancel" to avoid DCC.