Costco offers its members the Optimum Nutrition Gold Standard 100% Whey Protein 6.4-lb. Bag in Chocolate or Vanilla from $41.99 plus $1.99 for shipping. (Non-members pay $3 more.) That's $3 under our June mention and the lowest price we could find by $25. It includes 90 servings, and each contains 24 grams of protein. Deal ends January 28.