apparently, the most expensive restaurant inside Expo serves Japanese cuisine, that's cheaper (10 euro) It's up to the Turkey Pavilion. Free tasting? For example, Coca Cola in front of his Pavilion, or French cheeses at Le Bistrot du Lion (Pad. France).
If you want a guide to tell you all this and always up-to-date — at least that's the promise — just download the app by Zomato, that will tell you motions for aperitif, Vegan and gluten free, giving the possibility to comment.