I couldn't find a current menu with prices

But I did find a 1955 menu which showed grilled cheese at 40c, giving a 3.3% inflation rate

Official CPI shows 4.0% inflation over that period

Although, I do have some doubts as to the quality of that later sandwich compared to the ealier. The 1955 menu lists for example Lobster thermidor for $1.15 which I very much doubt could be had for under $6 in 2003