Carrefour. Lavazza Espresso Italiano two packs (2 x 250g) cost a little less than five euro here in France. Illy in its aluminum can on the top shelf works out to a little less than double that per kg.

It was cheaper in Spain, I recall. More like €1.80 for a 250g bag (cheaper still for Bonka, which you need to buy at least once just for the awesome name).