You played a smart move and know what to do next time. I have a feeling because you are in transit on the other side of security you and the businesses are treated as international and those businesses actually pay the airport who rents the space in dollars. I know local airlines here who fly to neighboring countries may have their tickets paid in local currencies, but all the airlines get paid in dollars via the government doing the forex. If that airport has local and international flights then this is classed as international land those businesses are situated on.