This feels like GasBuddy, but for food. One of the reasons GasBuddy took off was that it wasn't just based on community reports; there was an incentive for gas stations themselves to accurately report their prices and keep them up to date. It seems like you're trying to discourage businesses from participating (e.g. by not accepting sponsored placements), and that will have implications for your growth rate. I think…
Not really. GasBuddy has a standard: price per gallon But this is just a map of the lower-priced items, which are available everywhere. You can find a cheap sandwich, bowl of soup, slice of pizza, or taco virtually anywhere. There is no corresponding standard point of comparison (no "gallon").
$/cal varies meaningfully between home cooking, Costco, Chipotle, fast casual, sit-down, frozen meals, etc.