In Cairns, inside vehicle temperature can reach 120 cel, most people jump into the hot car, turn on the A/C and drive away without giving it another thought.
Every vehicle is fitted with a recircualtion/vent switch. There is a reason for this. When you get into the hot vehicle you should wind the windows down, put the vent on fresh and run until the majority of hot air inside the vehicle is despirsed. you will feel it when it's cooler, then wind the windows up and put on recirc.
By turning on the AC and recirculating hot air this puts more stress onto the engine as the AC compressor takes longer cycles to cool the cabin of the vehicle. This means more stress on the AC system, more stress on the engine and more fuel used to cool the car. The fuel used to cool when on recirc is excessive, it may cost you only 30 cents extra but think of that cost when you stop and start over a 6 month period. Makes sense to operate the AC the proper way than to pour your money down the drain.