The only way to have a completely automated restaurant is have a big box that spits out meals. The alternative is no automation or a lot of little boxes that are used for pieces.
The thing is that a restaurant would still needs counter-help and clean-up help so further. Let's assume the box reduces the cost of prep-labor by 50%. That reduces the labor past of your costs by 25% and your total costs by 12.5% assuming labor is 50% of costs. So it's a good savings but not an astronomical savings. But the counter-weight you have sell people on buying the food that comes out of the box. A few places compete on price alone but that's hard. Just consider that restaurants are already competing with microwave dinners in the frozen section that quite possibly are already spat out of a better, cleverer box at a central factory. It would seem restaurants compete on ambiance and human relations and a 12.5% prices savings might not compensate.
Another thing about "food out of a box" restaurant is that the box might not have the flexibility of a human preparer. If you need to change your menu, you might find you have to do expensive retooling on your box rather than a quick retraining of your employees. If you have to close a given restaurant, you may find no one wants your box. You may find yourself more dependent on your small number of box-technicians than you were previously on a large number of easily replaced unskilled cooks and so-forth.
The thing is that humans are a fabulous deal once you remove the price differential. Human comes with amazing skills, often train themselves with more, supervise and trouble-shoot each other, require little capital investment and manufacture themselves. This kind of thing is a good deal for nearly everything except production at a large scale (and the most important items, cars and iphones, are going to that large scale). The only unfortunate thing from the buyers perspective is that humans have a nasty habit of expect a share of the output instead of just a bare wage. But the solution to that problem is visible all around us ... humans.