See how purchasing a Costco membership can pay for itself for those feeding their family a whole foods diet. Robyn Openshaw from GreenSmoothieGirl.com will show you what she buys at Costco each week and how she gets her moneys worth from her yearly membership fee by purchasing quality fruits and vegetables and other whole foods items at Costco.  When she bought the yearly membership in 100 dollars, she got back 95 dollars. Hence, her net cost for membership purchasing was only 5 dollars.The food items are also very cheap at Costco (except for a few ones). A big spinach bag costs around half the price as compared to other grocery stores. Spinach is something which your kids need the most for their proper growth. Mixed frozen berries also cost around half the price as compared to other grocery stores. It not only tastes great, but is a great ingredient for smoothies. Bananas cost around one-third the price as compared to other grocery stores. A 6 pound bag of strawberries will cost you very less as compared to other grocery stores. Same is with pears, rice dream, vanilla, vanilla beans, oranges, papaya, and natural sweeteners. But, some items at Costco is not cheap. However, you would buy them from Costco because of their high-quality. They are: avocados and tomatoes.