What you are looking at is a cross border drop-off. Some rental company process this as a special ca

We are planning a trans Atlantic cruise, Miami to Barcelona in April 2013. We also wish to visit London and Paris after the conclusion of the cruise. The cruise ship company is paying our return airfare to the U.S. and we must depart from the port the cruise ended, which is Barcelona. We've been told to fly to London, then take the train to Paris. We would like to tour the French countryside on our way to Barcelona, however we can't find a car rental company free airline miles credit card that will quote prices from Paris with a drop off in Barcelona.
I'm sure there are a number of companies that would be happy to quote a price for pickup in Paris and dropoff in Barcelona - AutoEurope and Kemwel just to mention two. But do you realize what a whopping fee you'll pay for pickup in one country free airline miles credit card and dropoff in another? If you want to tour the French countryside, fine, just figure out how to drop the car off on the French side of the border (Perpignan, maybe) and get yourself to Barcelona on a train.
What you are looking at is a cross border drop-off. Some rental company process this as a special case and requires a phone call to find out the drop-off charge. If you just want to get an idea, Hertz tells you how much they cost. It looks like you might be paying about 300EU premium for the cross border drop-off going thru them. Dropping off at Perpignan is cheaper, but you have to add back about 33-40EU/person train fare.