Rental price was eventually 514 euro although in the reservation it was estimated about 240 euro. I made a reservation for an Opel Astra wagon (or similar) but the officer at the desk started to offer me an Audi A6 without saying nothing about the price! When I said that an A6 is very far from an Astra and I don't want to pay extra costs, I finally got an Opel Grandland X... So obviously it doesn't matter at all what you reserve; you just get whatever is available. Also in the final invoice there was an item of "Sonderreinigung" for 30 EUR ever though the vehicle was returned in very normal condition.