Air France, American Airlines, and British Airways have round-trip flights from Chicago (ORD) to Paris (CDG) for $474, NONSTOP. Flights November to March. Departures on Tuesday, Wednesday, and Sunday. 7-day minimum stay required.
Carry-on bag is allowed for free.
Note: There are “cheaper” flights on TAP for $314, but those fares require a connection and they charge about +$75 each-way to check a bag. After the fees and dealing with the extra stop, we don’t think those TAP fares are worthwhile. TAP fares are more expensive once you add the extra $150-ish and extra airport downtime to the base price.