I think Tartiflete was avaialble from one of the independent stalls down towards Tetre Rouge from Dunlop Bridge, if memory serves me right about 8 euro, not that I had any.
There was a survey in yesterdays metro on cost of attending Festivals including food and beer, and Le Mans would have outpriced them all. Not sure about F1 have not been for years. I know when I used to go to Silverstone and Brands Hatch the prices were high but not unreasonably so, and the circuits deliberately set them that way.