The 17 Eurozone members use the same currency, the "Euro", however 20 euros goes very far in certain EU members and it will get you nowhere in other EU member countries. For example, with 20 euros in Greece you can purchase 7 coffees, while in Portugal with the same 20 euros you will buy 30 cups of coffee. You get the idea.

20 Euros = 7 cartons of eggs in Ireland
                16 cartons of eggs in Malta

20 Euros = 4 pairs of socks in Belgium
                19 pairs of socks in Slovakia

20 Euros = 8 bus passes in Holland              
               43 bus passes in Slovakia

20 Euros = 6 liters of beer in Italy
                20 liters of beer in Slovakia

20 Euros = 1,6 kg cheese (camembert) in Slovenia
                 3 kg cheese in Belgium

20 Euros = 2 movie tickets in Ireland
                 8 movie tickets in Slovakia

20 Euros = 2-3 cigarette packs in Ireland
                 10 cigarette packs in Estonia

20 Euros = 30 newspapers in Malta
                 11 newspapers in Cyprus (England is not part in Eurozone, for 20 euros you can purchase 57 newspapers). 

20 Euros = 7,2 km distance with Taxi in Holland
                 23 km distance with Taxi in Portugal (70 km distance with Taxi in Bulgaria)

20 Euros = 2 liters of olive oil in Slovenia
                 7 liters olive oil in Spain

20 Euros = 24 pints of beer in a bar in Portugal
                 5 pints of beer in a bar in Ireland

20 Euros = 5 bottles of red wine in Italy
                20 bottles of red wine in Portugal

20 Euros = 242 tea bags in Austria
                 704 tea bags in Malta