At Trader Joe's there is the "Trader Darwin" Unsweetened Vanilla Soy Enriched Protein. It is $11.99 for 28 servings, 120 calories for two scoops and 22 grams of protein. It has no artificial sweeteners, which I like too. I mix it with unsweented soy milk...vanilla is good to buy also or the unsweetened chocoloate soy is tasty for a change.
You can add frozen banana or fruit (strawberries, pineapple, peach, etc) for some added fiber/flavor. I have found this to be the best one out there for taste, affordability, enriched vitamains and the fact there are no artificial sweeteners or fillers. I love Trader Joe's.