Although Im not in SF, I still think you have an interesting idea. My concern for you would be the actual product the chef's produce once you start getting some traction. The more a chef cooks in larger scale, the quality of the product goes down.

As a side night on your business model, I would have the chefs use ingredients that are readily cheap. This way your decreasing your startup costs and at the same time still increasing customers willingness to pay. Just a thought...goodluck. Im in Chicago and I would try it, if it were here.