I realize this is an old thread, but I just want to note that I've rented cars many times in France, Spain, and Germany, and I've never had to pay a one-way drop off charge as long as I picked the car up and dropped it off in the same country. I would guess there could be rental companies and maybe some remote locations where you might have to pay such a charge, but I've never had that experience.
I usually rent through gemut.com or autoeurope.com and have ended up with cars from various agencies--Hertz, Budget, Alamo, Europcar, and others. Last year was the last time we rented (in France). Again, never had to pay a drop off charge as long as we picked up and dropped off in the same country.
We avoided a $100 dropoff charge a few years ago by dropping our car in Lindau, Germany and taking a train from Bregenz, Austria to Zurich, Switzerland instead of driving to Zurich and dropping off there.
In retrospect, I would rather have paid the $100 so we could have stopped at various sights along the way instead of watching them whiz by from the train.