Uber isn't exactly cheap, just cheaper than taxis, which are super-expensive. Kitchen work generally requires some kind of training, often some kind of licensing or certification, and is rarely the cheapest type of labor.
Anyway, the main issue here is population density, not labor availability. If there tens or hundreds of thousands of people working and living in a quarter mile radius and average foot traffic was in hundreds or thousands per hour rather than dozens or less it would likely be easy to sell $4 bowls and make a profit - most of the US is vastly less dense and walkable than that though, even in cities.
Anyway, the main issue here is population density, not labor availability. If there tens or hundreds of thousands of people working and living in a quarter mile radius and average foot traffic was in hundreds or thousands per hour rather than dozens or less it would likely be easy to sell $4 bowls and make a profit - most of the US is vastly less dense and walkable than that though, even in cities.