Been 3 times and say around £700-£1000 depending on how many laps you do. That was splitting the 'road' petrol 50/50 with someone else, aswell as the hotel, and I did 22 laps last time I was there, heading down on the friday morning, returning tuesday night.

Try Villa Huegel for somewhere nice to stay, its literally 300 yards from the track entrance and its shit hot. I've also stayed in Hotel Zur Burg, almost as nice and as close to the track entrance. Both aren't cheap places but if you want to walk into nurburg for some beers of a night time, or walk to the track to watch its ideal!