It depends on what you want to do Didz.

Hotel for 4 nights (room & Breakfast only) about 300 - 330 euros per double / twin
Laps on the Ring (this year) 4 laps at 88 euros / single lap @ 24 euros
Petrol just getting there and back is 2 tanks each way
Ferry at about £40.00
European Insurance with re-patriation at £75.00 for the year.
Ring insurance depending on your insurance company ???

Food wise, we spent under 40 euros per person at the AM Tiergartten on the Saturday night including drink. Otherwise , drinks, evening meals at the hotel and lunches wherever allow about another 200 euros.

If you are going on your own, it's an expensive trip for sure. But with either a partner or wingman, it dramatically decreases the cost per person.

Hope that helps?

Steve