Well, really, I don't know how to tell you and less if there is no photo to see how the car is, anyway, if the car has the insurance in order, an expert can be seen to see it and to appraise what the blow is worth.
You already know that these things are sometimes not only what they see themselves, and I tell you that Renault to get the five stars in the Euroncap has resorted to make their "very soft" cars to absorb the impacts well, this translates into the minimum porrazo, they are discouraged whole because many pieces such as the fins are polycarbonate.
The card is usually expensive because you have to take it to Renault to verify the reader and others.
So the seller or makes you a good reduction or passes from the car. Turn around
www.segundamano.es and look for a megane like the one they sell you, calculate the difference and you have the account of whether it is worth it or not.
All the best.