Anything from a few Euros in France to Euro 250 at the bigger airports. The most I have paid was E 250 at Tirana (LATI) and E 100-200 is pretty common e.g. Prague.
The most you can pay is about E 800 at say Gatwick EGKK.
I think the average for the UK "GA-only" airfields is about E 15 (£10).
E80 (e.g, Norwich EGSH or Bournemouth EGHH) is unfortunately becoming more common, and while this is fine for the occassional flight it would be very expensive if one was doing it regularly.