Costco offers its members the Optimum Nutrition Gold Standard 100% Whey Protein Powder 6.4-lb. Bag in Chocolate or Vanilla for $44.99 plus $1.99 for shipping. (Non-members incur an additional $3 surcharge.) That's the lowest price we could find by $24. It includes 90 servings and each contains 24 grams of protein. Deal ends June 25.