Amazon sells Optimum Nutrition Gold Standard 100% Whey Protein Powder, Coffee, 5 Pound for $57.99
Clip 20% coupon on the product page and select Subscribe & Save option to get another 5% off and free shipping. The final price is $43.39 (or, if you have 5+ subscriptions this month, $37.69)
Applies to other flavors as well.
Also, applies to ON Casein and Syntha-6 proteins.