Mango price fluctuations

I have a question for Mango airlines. Yesterday I went to a store to purchase a return air ticket from Bloemfontein to Cape Town leaving 21/8 and returning 23/8. The quoted price was R883 both ways. When I wanted to pay Mango was off-line. After making sure that Mango was on-line I went to buy the ticket. Much to my surprise the ticket price for the ticket to Cape Town increased by a whopping R578!!! Can someone please explain this dramatic rise to me???? Why were they off-line - just to increase the price????