When my wife and I went back to the U.S. this past May to get our "proper" visas and jettison most of our household goods, we only needed one-way tickets back to Paris.
When we started looking online last autumn, the prices for one-way tickets were insanely high. Added to that, we were thinking we'd each be bringing about 100 pounds of check-in luggage, which in turn would add who-knew-what to the cost. So we started considering other options.
It turned out that traveling by cargo ship was financially competitive. Considering we would be getting two weeks of room and board with the price, it was actually less expensive than flying directly back to Paris and paying room and board here.
So that's what we did: we took a cargo ship from Baltimore, Maryland to Hamburg, Germany, and then rented a car and drove down to Paris. And again, all things considered, it was less expensive than it would have been to fly.
I kept a pretty detailed journal, and later turned that into an online travelogue. I am posting the link in case anyone might find themselves looking for alternatives to flying into or out of France from the U.S. or elsewhere:
Diary of a Cargo Ship Voyage