I agree, there are still ways to sell your food cheap though. A good example is a vegan/vegetarian burger place near me. Demand for that kind of food is high because it's a liberal college town, but that restaurant is the only one of its kind here, so it's always full. Also they sell more fancy, more expensive dinner options in the evening which I'm sure subsidizes the cheap burgers. And if you mainly go there for their burgers you might return for dinner sometime to try out those options. They've existed for around 10 years now and their cheapest burger has stayed at 4,50€ that whole time.

Granted it's hard to know what kind of demand there is in your town without trying some stuff and maybe failing.