You're a bit late for cheap flights around final closing party week, they almost never drop in price from now on and supply is less than right now for example overall. Been cheaper booked months ahead for years now, especially returns from the island.
September is also a nightmare for getting cheap tickets late in the day, last-minute prices can be really stubborn it's been much easier in August to get cheap tickets last minute for the last few years. But that's balanced out by really stupid hotel prices and trouble getting somewhere for any length of time without having to move hotel.