Searched for the menu gap term on Google and 'gap' term on Namebio to check the possibility. Based on the analysis, the number of sales, search results and price of each sale, it doesn't look very encouraging. Menu gap doesn't have a commercial product as such and that makes me a bit skeptical that it would be priced very high. Hence, I don't think this would be a popular term among buyer. So, I'd say $0 for this name.