Now that I am an expert on reading popular books on economics, I understand the world a lot better. For example I didn't expect that my local supermarket would close at 16:00 on New Years Eve. As I walked into town through the freezing fog, I thought, no doubt all the other supermarkets will be closed too. And yes they were, even the supermarket at the Wuppertal train station, that usually stays open late, was closed.
Anyway the "off licence" near the station was still open, so I could buy beer. I paid 6 Euros for 4 cans of bier, rather than the 4 Euros I would have paid at a supermarket. Supply and demand in action!