If you are buying milk at the market, it is definitely not to find Costco prices. You are probably at a dairy farm's booth because you want milk from cows who have not been given growth hormones to increase milk production. You can also buy the milk in returnable glass containers, thereby helping the planet and well as the cows. (Fat-free milk is available.)
There's a bit of a controversy at the market about organic certification. Some growers feel that what is required for them to qualify as organic does not address the issues they face as they employ many healthy farming practices. Some feel they go above and beyond the rules of being organic, and that the certification is not as meaningful as many think. The best thing is to ask the vendor how the food you are about to purchase was grown. Most seem extremely forthcoming and happy to explain their methods.Some people go to the market for the superior freshness of items availalble throughout the city, just not at this quality. Have you ever tried to buy wild mushrooms and been discouraged by the moldiness or broken pieces of the display at your local supermarket? Some of the mushrooms are probably even pre-wrapped in plastic, possibly the worst thing for them. Here they are beautiful, and you are sent off with your mushrooms in a paper bag, which is just how you should be storing them in the fridge.
Although the market is best known for the quality of its produce than low prices, there are the occasional bargains, such as these apples. Shopping toward the end of the day can also lead to price breaks, but is risky, since many items disappear by early afternoon.