Not surprised to be honest, prices have crept up over the last few years as far as I am concerned. I did not go this year, decided to have a year off, but will be back next year. I thought the burgers and bacon baps by some of the British companies last year was poor quality and massively over priced. They were situated just outside Blu Nord.
A friend of a friend was at Le Mans a few years back, he has his own mobile catering. He did not take the option of going back, as the profit was only about £12K for the weekend. Apparently it was n't worth the effort.