Was watching the episode of Top Gear when Clarkson took the Diesel Jag around the ring. He said it was €14 a lap.
Just looked at the latest prices:
2009 Price in Euros
Single lap €22
4-lap ticket €75
8-lap ticket €145
15-lap ticket €250
25-lap ticket €390
66 laps Breakeven point for a Jahreskarte
Jahreskarte €1,075