American Airlines has round-trip flights from Houston (IAH) to Nice or Marseille (NCE/MRS) starting at $496 with a connection. Flights in February, March, October, November, December, and January. No minimum stay required, but New Years is available in Nice if you can stay longer than 10-days.
Note: Fare allows for free carry-on bag, but a checked bag will cost +$60 each-way. Upgrades into “Regular Economy” are available for +$55 each-way. You can avoid paying a seat selection fee by accepting the randomly assigned seat at the gate.