If you're flying day/VFR about Europe, its generally a good idea to avoid large airports, especially those running close to their capacity. They see no value to themselves in GA traffic and will price it out if possible.
Under Schengen agreement, international travel using small fields is generally much easier; no battling with airport security and much lower costs.
That said, I would expect to pay 20-30 Euros to land at a well equipped field with lights, instrument approaches, customs etc., and more like 10-15 euros at smaller fields with fuel, planning and food available, for most of northern Europe.
Outside parking is usually a similar order to the landing fee per 24 hrs with the first 3-6 hours free.
Italy probably has about the most expensive Avgas in Europe; Denmark and the Channel Islands about the cheapest.