I complained to the publisher to the 17€ (!) they charged me to send it to France while someone in Belgium got charged 7€ less. They answered me :
"You are right, it´s difficult to understand. We get the cheapest charges for Belgium, the Nederlands, Luxemburg and Austria, the secondcheapest for Denmark, Check Republik and Switzerland and on the third place for France, Great Britain and Monaco."
So if you are in France, as I will do next time, buy from Lela Presse :
http://www.avions-bateaux.com/