Amazon offers the Optimum Nutrition Gold Standard 100% Casein Protein Powder 4-lb. Jar in French Vanilla for $52.03. Check out via Subscribe and Save to drop the price to $49.43 and bag free shipping. That's the lowest total price we could find by $4, although we saw the same quantity of a different flavor for $12 less in March.
Be sure to cancel Subscribe & Save once your order ships or you'll be billed for subsequent shipments.