Amazon has a $1 coupon for Pure Protein® Chocolate Peanut Caramel protein bars, 50 gram, 6 ct
Combine it with Subscribe & Save option to get another 5% off and free shipping.
The final price is $5.11 (or, if you have 5+ subscriptions this month, $4.47)
This is less than a dollar per bar. Each bar has 20 grams of protein, 190 calories and 2 grams of sugar.
Warning: they taste amazing and are very addictive.