Just off ZL145, the 1730 SYD-MEL, had 28 pax on the flight, booked a $79 fare on Thursday, when the cart came along I ordered a beer ($7) and gave the FA a 10, said she would be back with the change, interestingly REX only accept cash onboard, no plastic. The FA came back 10 mins later said they didn't have any change as I was the only person to have bought something and gave me my $10 back, so that's another $7 the flight lost, but I got a cheap ticket and a free beer.
