Yes, it will be cold here. Please wear wollen sweater and overcoat. It is difficult to say whether the good price in Shanghai is more expensive or not. The food should be cheaper if you eat at a local restaurant. The goods in these top class department stores should be expensive, but this is the same all over the world. But, these goods for daily life is reasonable. You could have a good meal there with CNY20~30/adult. Of course, you could find many nice restaurants as well, costing CNY200~300.