Whilst not WOW air $200 return... there is pretty consistent availability MAN-MIA via PHL on the way out, LHR on the way back for £350 each. With BA/AA so includes 23kg luggage, food, and if you pick the AA operated legs, free seat selection for "regular" seats. Wide open in September and October, disappears over the winter season, comes back in April after Easter into June 18. I've chosen to do this for my TP Run to get my 4 qualifying flights and 30TPs (although this routing will actually get you 50TPs) Any good - or am I completely mad going to Miami for 4 nights on a TP run...
Clearly at least mildly eccentric (read: bonkers) by any 'normal' standards, but you'll get nothing but hearty congratulations from me (or anyone else in these parts I suspect)! Very decent price that btw!
We paid £466 return for LHR-MIA direct, travelling last July, so it seems a reasonable price. I can heartily recommend "The Front Porch Cafe" on South Beach for lunch or dinner, really excellent.