I recently came across this NYTimes article explaining how best to game the salad bars at your local supermarkets. It's nothing really groundbreaking. It's relatively obvious that walking away from the salad bar with a carton full of the most expensive ingredients (sun-dried tomatoes, bacon bits, perhaps some cheeses and fruit) will save you money compared to buying those ingredients elsewhere in the store. I have evaluated the opportunity at my supermarket, but rejected it for several reasons.
One very clear reason is that my price threshold for nearly all food that I buy is still lower than the salad bar price. I just don't pay that much for any food. There are three things (besides spices and teas) I will pay more than $5/lb for: sea scallops, premium cheeses, and premium chocolates, and I do not buy them often. I get my premium cheeses at Trader Joe's for half the price the supermarket charges. I am able to feed myself a variety of good foods for less than the price of salad bar food, so I am not motivated to get salad bar food even though there is an opportunity to get a couple items at a discount.
There are reasons for people with higher price thresholds to avoid or minimize gaming their salad bars, too. Commenters of a blog post on the NYTimes article express real concerns that exploitation of salad bars results in the loss of valuable ingredients or even the whole bars all together. There is a tragedy of the commons, and morality comes into play. Salad bars are expensive because of waste, labor, and maintenance, which the stores take on so that customers don't have to. Customer behavior that throws off the balance of the system can have consequences to other people
Gaming the salad bar as the article describes is primarily about getting your money's worth with your salad, not just walking away with a bowl of sun-dried tomatoes. Of course, you can make your own great salads for much less money by buying romaine, spinach, etc... and spending a few minutes chopping and slicing. People with money get salads at salad bars for the convenience, and the rest of us trade inconvenience for cost.