American and British Airways have round-trip flights from Dallas (DFW) to Nice or Marseille (NCE/MRS) for $535-$555. Flights from September to May. Expect prices to fluctuate by +/- $20.
Note: Fare allows for a free carry-on bag, but checked-bag and seat selection will cost an additional fee. Travelocity has “Regular Economy” tickets available for $578. ($569 basic fare + $9 upgrade)
Note: Book on Expedia or Travelocity. Other sites seem to be more expensive at the moment.
Note: Stick closely to the example dates for this deal to avoid long connection times.
Note: New Years Eve is available if you can do 9-day stay or longer.