Five Minute Late arrival - R750 Penaltiy

I arrived at OR Tambo @ 05:25 to check in for my flight back to Cape Town on Monday morning, the supervisor was still stranding at the check-in point, but I was told that the gates had just been closed. the depart time was 05:55 am the plane was still parked in the airport and there where 3 other ladies behind me to board the same flight. The airport staff did nothing to assist us tp try and help, we were advised to report to the sales desk to assist us further. I was charged a Penaltiy of R750.00 for Five minutes, the other lady was charged R900.00 for her late arrival. The assistant that assisted me, stated that there was only one seat available for the next flight that was leaving at 08:10am. I rushed to pay the penaltiy, because of the other 2 ladies also in- waiting, only to get onto the plane to see that theree were +10 seats still available and the other two ladies were already on the plane. When leaving Cape Town The Thursday evening prior to this I arrived 10 minutes before departure time and was still allowed to board my flight in Cape Town. I do not get this. <br> This airline advertises to be the cheapest airline going, but the charge tou a R150.00 per suitcase...ect